The MediaWiki installation at http://co-op.downinthecountry.com/wiki has session ID issues. The session ID written to php_sessions has "sess_" prefixed to it; the session ID sent to the browser does not.

Thus, it is impossible to remain logged in.

Can someone aim me at possible causes? It's a vanilla install; php version 5.2.5.

First install was mediawiki-1.14.0; now running mediawiki-1.15.0rc1. Both had the same issue.

TIA.