Thread:Project:Support desk/Fatal error tring to login under 1.18.1

Upgrading from mediawiki 1.17.2 to 1.18.1, get the following message when now trying to log in by clicking on the upper-right link:

Fatal error: session_start: Failed to initialize storage module: user (path: /tmp) in /usr/local/apache2/htdocs/wiki/includes/GlobalFunctions.php on line 3108

The upgrade process: move the old wiki to another directory, install the new one clean into its own, run maintenance/update.php from the command line (no errors present). Then moved LocalSettings.php, some extensions and the image directory's contents over to the new wiki.

The wiki comes up fine, is perfectly navigable, but won't allow the log in link to work any more. Even defining the session save path to /tmp doesn't solve the problem. Any ideas? Going back to the old version everything works as before.

Stats:

php: 5.2.17 postgres: 9.1.0

please and thanks