diff --git a/lib/base.php b/lib/base.php
index cfcfb94af80e4d4f0617fe1d2a18d55e6e874d3f..71e2ed63888aebc0e2be6d0428dfe2f93a7d41be 100644
--- a/lib/base.php
+++ b/lib/base.php
@@ -128,7 +128,7 @@ class OC{
 		// calculate the documentroot
 		OC::$DOCUMENTROOT=realpath($_SERVER['DOCUMENT_ROOT']);
 		OC::$SERVERROOT=str_replace("\\",'/',substr(__FILE__,0,-13));
-		OC::$SUBURI=substr(realpath($_SERVER["SCRIPT_FILENAME"]),strlen(OC::$SERVERROOT));
+		OC::$SUBURI= str_replace("\\","/",substr(realpath($_SERVER["SCRIPT_FILENAME"]),strlen(OC::$SERVERROOT)));
 		$scriptName=$_SERVER["SCRIPT_NAME"];
 		if(substr($scriptName,-1)=='/'){
 			$scriptName.='index.php';
@@ -438,7 +438,7 @@ class OC{
 		register_shutdown_function(array('OC_Helper','cleanTmp'));
 		
 		//parse the given parameters
-		self::$REQUESTEDAPP = (isset($_GET['app'])?str_replace(array('\0', '/', '\\', '..'), '', strip_tags($_GET['app'])):OC_Config::getValue('defaultapp', 'files'));
+		self::$REQUESTEDAPP = (isset($_GET['app']) && trim($_GET['app']) != '' && !is_null($_GET['app'])?str_replace(array('\0', '/', '\\', '..'), '', strip_tags($_GET['app'])):OC_Config::getValue('defaultapp', 'files'));
 		if(substr_count(self::$REQUESTEDAPP, '?') != 0){
 			$app = substr(self::$REQUESTEDAPP, 0, strpos(self::$REQUESTEDAPP, '?'));
 			$param = substr(self::$REQUESTEDAPP, strpos(self::$REQUESTEDAPP, '?') + 1);