I currently run DT Pro Office 2.5.2 on a MacBook Air with Mac OSX 10.8.3
There has been a (relatively) recent change in expected window behaviour after use of the See Also and Classify Drawer.
While Document windows still return to their original positions after the Drawer is closed, Group windows do not. The anomalous behaviour occurs in both Full Screen and normal.
I have seen this from time to time on 10.8.x on a MacBook Air. Usually a reboot clears it. It seems to have something to do with desktops (spaces) – lots of switching between spaces can precede the behavior @Gildor described, over here, but I cannot reliably reproduce the problem. Try the reboot.