I hope this gives you plenty of information.
Pages that work:
/wiki/Special:Categories /wiki/Special:AllPages /index.php?title=Category:Videos&action=edit&redlink=1
Don't work:
/wiki/Category:Videos (After submitting the changes to the 'Videos' category. /index.php?title=Category:Videos
The error:
When looking at Videos category:
Warning: mysql_real_escape_string() expects parameter 1 to be string, object given in /usr/local/www/wiki/includes/db/DatabaseMysql.php on line 331
Notice: Undefined property: CategoryWithVideoViewer::$context in /usr/local/www/wiki/extensions/Video/VideoPage.php on line 381
Catchable fatal error: Argument 2 passed to Video::__construct() must implement interface IContextSource, null given, called in /usr/local/www/wiki/extensions/Video/VideoPage.php on line 381 and defined in /usr/local/www/wiki/extensions/Video/VideoClass.php on line 119
When looking at any other category:
Warning: mysql_real_escape_string() expects parameter 1 to be string, object given in /usr/local/www/wiki/includes/db/DatabaseMysql.php on line 331
Fatal error: Cannot use object of type RequestContext as array in /usr/local/www/wiki/includes/CategoryPage.php on line 712
Information on my instance:
MediaWiki 1.18.0 PHP 5.3.5 (cgi-fcgi) MySQL 5.5.9
Extensions:
Nuke (Version 1.1.3) (r107592) Password Reset (Version 1.7) (r107592) Renameuser (r107592) Gadgets (r107592) Video (Version 1.4)
Edit: I just confirmed that the error also occurs with only the Video extension installed.