diff --git a/apps/user_ldap/group_ldap.php b/apps/user_ldap/group_ldap.php
index 2c16bf312f..baca1d32ba 100644
--- a/apps/user_ldap/group_ldap.php
+++ b/apps/user_ldap/group_ldap.php
@@ -31,8 +31,8 @@ class OC_GROUP_LDAP extends OC_Group_Backend {
 		$this->ldapGroupFilter          = OCP\Config::getAppValue('user_ldap', 'ldap_group_filter', '(objectClass=posixGroup)');
 		$this->ldapGroupMemberAssocAttr = OCP\Config::getAppValue('user_ldap', 'ldap_group_member_assoc_attribute', 'uniqueMember');
 
-		if(empty($this->ldapGroupFilter) || empty($this->ldapGroupMemberAssocAttr)) {
-			$this->configured = false;
+		if(!empty($this->ldapGroupFilter) && !empty($this->ldapGroupMemberAssocAttr)) {
+			$this->configured = true;
 		}
 	}
 
diff --git a/lib/filecache.php b/lib/filecache.php
index a94349e19c..a29e29928a 100644
--- a/lib/filecache.php
+++ b/lib/filecache.php
@@ -419,7 +419,7 @@ class OC_FileCache{
 			}
 			return $result;
 		}else{
-			OC_Log::write('files','getChached(): file not found in cache ('.$path.')',OC_Log::DEBUG);
+			OC_Log::write('files','getCached(): file not found in cache ('.$path.')',OC_Log::DEBUG);
 			if(isset(self::$savedData[$path])){
 				return self::$savedData[$path];
 			}else{
diff --git a/lib/log/owncloud.php b/lib/log/owncloud.php
index 0b7a231d30..5913d8b5b8 100644
--- a/lib/log/owncloud.php
+++ b/lib/log/owncloud.php
@@ -62,23 +62,26 @@ class OC_Log_Owncloud {
 	public static function getEntries($limit=50, $offset=0){
 		self::init();
 		$minLevel=OC_Config::getValue( "loglevel", OC_Log::WARN );
-		$entries=array();
-		if(!file_exists(self::$logFile)) {
-			return array();
-		}
-		$contents=file(self::$logFile);
-		if(!$contents) {//error while reading log
-			return array();
-		}
-		$end=max(count($contents)-$offset-1, 0);
-		$start=max($end-$limit,0);
-		$i=$end;
-		while($i>$start){
-			$entry=json_decode($contents[$i]);
-			if($entry->level>=$minLevel){
-				$entries[]=$entry;
+		$entries = array();
+		$handle = fopen(self::$logFile, 'r');
+		if ($handle) {
+			// Just a guess to set the file pointer to the right spot
+			$maxLineLength = 150;
+			fseek($handle, -($limit * $maxLineLength + $offset * $maxLineLength), SEEK_END);
+			// Skip first line, because it is most likely a partial line
+			fgets($handle);
+			while (!feof($handle)) {
+				$line = fgets($handle);
+				if (!empty($line)) {
+					$entry = json_decode($line);
+					if ($entry->level >= $minLevel) {
+						$entries[] = $entry;
+					}
+				}
 			}
-			$i--;
+			fclose($handle);
+			// Extract the needed entries and reverse the order
+			$entries = array_reverse(array_slice($entries, -($limit + $offset), $limit));
 		}
 		return $entries;
 	}
diff --git a/lib/setup.php b/lib/setup.php
index 8c2d523121..a096fdbb4c 100644
--- a/lib/setup.php
+++ b/lib/setup.php
@@ -94,6 +94,7 @@ class OC_Setup {
 						'error' => 'MySQL username and/or password not valid',
 						'hint' => 'You need to enter either an existing account or the administrator.'
 					);
+					return($error);
 				}
 				else {
 					$oldUser=OC_Config::getValue('dbuser', false);
diff --git a/lib/user.php b/lib/user.php
index d7e9bf1a64..17c11322b8 100644
--- a/lib/user.php
+++ b/lib/user.php
@@ -21,7 +21,9 @@
  */
 
 /**
- * This class provides all methods for user management.
+ * This class provides wrapper methods for user management. Multiple backends are 
+ * supported. User management operations are delegated to the configured backend for
+ * execution.
  *
  * Hooks provided:
  *   pre_createUser(&run, uid, password)
@@ -240,7 +242,7 @@ class OC_User {
 	 * Checks if the user is logged in
 	 */
 	public static function isLoggedIn(){
-		if( isset($_SESSION['user_id']) AND $_SESSION['user_id'] ){
+		if( isset($_SESSION['user_id']) AND $_SESSION['user_id'] AND self::userExists($_SESSION['user_id']) ){
 			return true;
 		}
 		else{
diff --git a/lib/user/backend.php b/lib/user/backend.php
index 3df907226c..c31d4b5785 100644
--- a/lib/user/backend.php
+++ b/lib/user/backend.php
@@ -40,8 +40,10 @@ define('OC_USER_BACKEND_USER_EXISTS',       0x100000);
 
 
 /**
- * abstract base class for user management
- * subclass this for your own backends and see OC_User_Example for descriptions
+ * Abstract base class for user management. Provides methods for querying backend
+ * capabilities.
+ *
+ * Subclass this for your own backends, and see OC_User_Example for descriptions
  */
 abstract class OC_User_Backend {
 
diff --git a/lib/user/http.php b/lib/user/http.php
new file mode 100644
index 0000000000..009aa30c6f
--- /dev/null
+++ b/lib/user/http.php
@@ -0,0 +1,93 @@
+<?php
+
+/**
+* ownCloud
+*
+* @author Frank Karlitschek
+* @copyright 2012 Robin Appelman icewind@owncloud.com
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+* License as published by the Free Software Foundation; either
+* version 3 of the License, or any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU AFFERO GENERAL PUBLIC LICENSE for more details.
+*
+* You should have received a copy of the GNU Affero General Public
+* License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+*
+*/
+
+/**
+ * user backend using http auth requests
+ */
+class OC_User_HTTP extends OC_User_Backend {
+	/**
+	 * split http://user@host/path into a user and url part
+	 * @param string path
+	 * @return array
+	 */
+	private function parseUrl($url){
+		$parts=parse_url($url);
+		$url=$parts['scheme'].'://'.$parts['host'];
+		if(isset($parts['port'])){
+			$url.=':'.$parts['port'];
+		}
+		$url.=$parts['path'];
+		if(isset($parts['query'])){
+			$url.='?'.$parts['query'];
+		}
+		return array($parts['user'],$url);
+		
+	}
+	
+	/**
+	 * check if an url is a valid login
+	 * @param string url
+	 * @return boolean
+	 */
+	private function matchUrl($url){
+		return ! is_null(parse_url($url,PHP_URL_USER));
+	}
+	
+	/**
+	 * @brief Check if the password is correct
+	 * @param $uid The username
+	 * @param $password The password
+	 * @returns string
+	 *
+	 * Check if the password is correct without logging in the user
+	 * returns the user id or false
+	 */
+	public function checkPassword($uid, $password){
+		if(!$this->matchUrl($uid)){
+			return false;
+		}
+		list($user,$url)=$this->parseUrl($uid);
+		
+		$ch = curl_init();
+		curl_setopt($ch, CURLOPT_URL, $url);
+		curl_setopt($ch, CURLOPT_USERPWD, $user.':'.$password);
+		curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+
+		curl_exec($ch);
+
+		$status = curl_getinfo($ch, CURLINFO_HTTP_CODE);
+		
+		curl_close($ch);
+
+		return $status==200;
+	}
+
+	/**
+	 * @brief check if a user exists
+	 * @param string $uid the username
+	 * @return boolean
+	 */
+	public function userExists($uid){
+		return $this->matchUrl($uid);
+	}
+}
\ No newline at end of file
diff --git a/lib/util.php b/lib/util.php
index be7fc00da8..fda60587b8 100644
--- a/lib/util.php
+++ b/lib/util.php
@@ -28,6 +28,14 @@ class OC_Util {
 			exit;
 		}
 		
+		// Check if apps folder is writable.
+		if(!is_writable(OC::$SERVERROOT."/apps/")) {
+			$tmpl = new OC_Template( '', 'error', 'guest' );
+			$tmpl->assign('errors',array(1=>array('error'=>"Can't write into apps directory 'apps'",'hint'=>"You can usually fix this by giving the webserver user write access to the config directory in owncloud")));
+			$tmpl->printPage();
+			exit;
+		}
+		
 		// Create root dir.
 		if(!is_dir($CONFIG_DATADIRECTORY_ROOT)){
 			$success=@mkdir($CONFIG_DATADIRECTORY_ROOT);
@@ -256,6 +264,9 @@ class OC_Util {
 		if(floatval(phpversion())<5.3){
 			$errors[]=array('error'=>'PHP 5.3 is required.<br/>','hint'=>'Please ask your server administrator to update PHP to version 5.3 or higher. PHP 5.2 is no longer supported by ownCloud and the PHP community.');
 		}
+		if(!defined('PDO::ATTR_DRIVER_NAME')){
+			$errors[]=array('error'=>'PHP PDO module is not installed.<br/>','hint'=>'Please ask your server administrator to install the module.');
+		}
 
 		return $errors;
 	}
diff --git a/settings/personal.php b/settings/personal.php
index 41499657ac..64e08be89e 100644
--- a/settings/personal.php
+++ b/settings/personal.php
@@ -20,6 +20,7 @@ $rootInfo=OC_FileCache::get('');
 $used=$rootInfo['size'];
 $free=OC_Filesystem::free_space();
 $total=$free+$used;
+if($total==0) $total=1;  // prevent division by zero
 $relative=round(($used/$total)*10000)/100;
 
 $email=OC_Preferences::getValue(OC_User::getUser(), 'settings','email','');
diff --git a/tests/lib/user/backend.php b/tests/lib/user/backend.php
index 5dab5afb18..984249e84e 100644
--- a/tests/lib/user/backend.php
+++ b/tests/lib/user/backend.php
@@ -20,6 +20,16 @@
 *
 */
 
+/**
+ * Abstract class to provide the basis of backend-specific unit test classes.
+ *
+ * All subclasses MUST assign a backend property in setUp() which implements 
+ * user operations (add, remove, etc.). Test methods in this class will then be
+ * run on each separate subclass and backend therein.
+ * 
+ * For an example see /tests/lib/user/dummy.php
+ */
+
 abstract class Test_User_Backend extends UnitTestCase {
 	/**
 	 * @var OC_User_Backend $backend