Desktop icons won't open

[Fredrik Jørgensen <fredrik jorgensen sensewave com>]

All launchers on the desktop are shown like '<appname>.desktop', and 
when I click on any icon on the desktop, Gnome can't figure out which 
program to use (which it used to figure out...)

I'm a newbie to Linux and Gnome, so please keep it simple ;)

Best,
Fredrik