[wlug] /usr/share/applications what am I doing wrong?

I've installed Padman and urban terror in /opt .. created scripts to launch them in /usr/games, put icons in /usr/share/pixmaps and created .desktop files in /usr/share/applications (by copying the one for openarena and just changing the names). So far so good, the games appear in the menu and I can play them. After a reboot they're gone from the menu for every user, but I can get them back in the menu by simply opening a root terminal, moving the two .desktop files from /usr/share/applications to another directory and then moving them back again. And nothing more than this is required. What is going on?!