Hanno Braun wrote: [snip]
The wiki is hosted at Sourceforge.net. sf.net uses multiple apache-servers to serve web pages. When a page is requested an apache is selected by some kind of load balancing mechanism.
[ship]
You need to set the session save path to a directory that's common to all servers instead of /tmp, which is on the local hard drive.
See: http://www.php.net/session http://www.php.net/ini_set
Note that Sourceforge's project web servers are deliberately configured in a very insecure way for a multiuser server farm; any other registered developer on any other project can read your session files, or use the database password in your LocalSettings.php to get into your project's MySQL database.
Due to the security situation I would recommend against running a wiki or any other database-driven or password-accepting application in your SourceForge project web space.
-- brion vibber (brion @ pobox.com)