Filemanager: XML Errors

Hello,

I get following error when I try to use the built-in filemanager from FCKEditor:
XML Request error: Unknown (12152)

I have set up the connector to PHP and changed the Userfile-path in the config.php. First I changed the Userfile-path to 'UserFiles/' (removed the / at the beginning, so the new location would be in the same folder where the script is) and created a UserFiles folder in the /connector/php/-path and in the directory, where the script is. This gives me the above error.
When I change the path to '/srv/www/htdocs/web254/html/UserFiles' (which is my home dir), I get "You have now permissions to create the folder".
When I change it to getcwd(); I also get "no permissions", even tho I made sure, they got CHMOD 777.

Can't find anything on the Internet about this problem

Thanks for taking your time