I'm running two websites on the same server (Apache 2.2.8 with PHP 5.2.5 and MySQL 5.0.51a-community) and viewing them with the same browser on the same computer (an iMac with Firefox or a Dell PC with MSIE). Both are running Zikula 1.0 and Content 2.1.0. On one when adding content I see the drop-down menu for selecting content type without a problem. On the other the drop-down menu never displays. As far as I can tell, both installations are the same. What could I have changed to cause the problem with the drop-down menu?
check your styles to see if something (positioning) is causing the menu to appear off screen.
Try changing your theme on the site that's having the issue.
If you use the Firefox webmaster toolbar, you can edit all of you css files and see the changes in real time.