There is an admin session problem present in the J! 1.0.13 release. Thanks to Rob Schley we now have a patch for it. See http://forum.joomla.org/index.php/topic ... #msg943504 for the patch or download it from this thread which contains a copy.

Instructions:

Just unzip the package, you will find two folders each containing one file. Simply upload the folders and files on top of your Joomla! installation as you do with any upgrade.

Important note:

You are advised to test this first, and make backups of the files which are replaced. The fix is a very recent one, and only a small amount of users have tested and confirmed it's fix.

Note: Users have to be logged in the forum to be able to download the patch.