Deleting ~/.gimp-2.8/sessionrc fixed the problem for me. There seems to be a bug that caused the file not to get updated. This caused the dialog windows to show up on the last saved location which was on another monitor. I can't investigate this problem anymore, because I deleted the file without any backup.
Here is something I found digging into the code. It turned out not to be the cause of the bug, but it's something which just makes you furious when it takes you hours to debug an issue like that. But hey, it's not a bug, it's a "feature" ^^ (from gimpsessioninfo.c): /* Window managers and windowing systems suck. They have their own * ideas about WM standards and when it's appropriate to honor * user/application-set window positions and when not. Therefore, * use brute force and "manually" position dialogs whenever they * are shown. This is important especially for transient dialog, * because window managers behave even "smarter" then... */ I wonder why gimp has to force window positions at all. The Window Manager I'm using would have chosen perfectly reasonable places for the dialog windows (well, I especially configured it to do that). -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org