Web admin interface fails to show pull down menus for game types (and susequently maps) after the game is relaunched. A work-around is to replace System/CacheRecords.ucl prior to starting the server with the original distribution file.
Just verifying, I see this too.
Here is a forum thread on unrealadmin.org about this bug. http://www.unrealadmin.org/modules.php?name=Forums&file=viewtopic&t=3043 Apparently UT2004 keeps regenerating the CacheRecords.ucl file in the System directory when you first access the web admin, however it's not doing it correctly and the webadmin fails to list the maps (which are pulled from this cache file). the fix mentioned up there is to chmod 444 the CacheRecords.ucl file, but then custom maps don't make it into the web admin list..
*** Bug 1485 has been marked as a duplicate of this bug. ***
This got fixed at some point. --ryan.