Happens to me too, but only if I start up anything else AFTER starting up the launcher. So if it's launcher -> play game nothing happens, but if it's launcher -> check something on the internet -> play game it does happen. Hope this helps.
On a possible similar note, when I am in the process of loading a game in windowed mode, the window moves right and down about 5 pixels. When the game has loaded, the window is moved back to its original position. Just an oddity I never would have thought to post about. I play DoD windowed 1600x1024.
Happens to me also, typically whenever this happens the launcher is taking its time to load up the game. Also running windows 7/64bit
On that note, when loading a save game, the window title becomes "Dungeons of Dredmor (not responding)". That is there for about 1-2 seconds and the game is loaded before Windows intervenes with a warning popup.
I confirm this. Happens when this conditions occur. I fix it going to the desktop with Alt+Tab and going back to the game. Give it a try, if you haven't already.