I use GNOME 99% of the time (CentOS 5.3 32 bit). I have never seen this. If the box has GNOME on it, in Nautilus, if you right click on the file name, it gives you the opportunity to select another app to open the file with. I have OO 3.1 installed.
It looks like I found the config in ~/.local/share/applications. Will wipe the user's desktop config files and prefs and let Gnome recreate them.