...Apparently QB tries to get an update (which it does not need, as it is the R4 version), so I am guessing it is triggered by some internet check. At any rate, it fails because it suddenly disconnects from the net. It throws up an error message that you only have 100 bytes on your disk and cancels the update. Sometime between the update cancellation and the program opening, IT DESTROYS YOUR DESKTOP FOLDER as it turns it into a text edit document instead of a folder. This wipes all content of your Desktop.
If you are riunning Leopard and Time Machine you can restore the desktop folder but the next time you run QB it will, again, destroy the desktop folder.
What I did was to move everything from my desktop fpolder into another folder at the root level of the hard drive. I did leave just one small file on the desktop. Now when I run QB it destroys my desktop and I open the .../users/<my name> folder and I throw away the ruined desktop folder which is now a generic icon. Then I start Time Machine and choose to restore the one small file -- Time Machines asks if I want to remake the enclosing folder and I answer yes and wind up with the desktop folder again and the one small file.
Obviously this is ridiculous to have to do. ...