Unable to reproduce on Win7, and I would be very surprised if I was able to. And even if I was able to reproduce it, I could probably not fix it, because OpenMPT's internal bitmap buffer will certainly never see the pixels of your desktop. To me, it looks like it might be graphics driver issue. To verify this, you could try to disable hardware acceleration temporarily (right-click desktop -> screen resolution -> advanced settings -> troubleshoot. If the button there is greyed out, you'll have to find out how to do this in your video driver's control panel.

I guess I was able to reproduce this, although the background remained grey and didn't show the desktop. I don't know why it should even do that.
In my observations, this bug may also happen when switching between several open modules.
Anyway, can you check if this build works better for you? http://sagagames.de/stuff/mptrack.exe

PS: You don't need to put your own issues on the monitoring list, you will get notified of any change to the issue anyway.

I did not know that, but thanks for the info. I am going to try the new build later, but it might boil down entirely to the graphics drivers.

In the days before we had the modern GPU, when we had separate 3D rendering cards and 2D rendering cards, and those had their own separate drivers. But once the GPU was invented, which combined the two, the quality of the 2D rendering component became much lower priority, which is why these kinds of bugs happen.

No it really, really isn't. That's just plain wrong (and irrelevant really). As I said, I can reproduce the bug and I know why it happens, I just don't get it to display content from a foreign window. The driver thing was just a first idea when I had no idea what was going on there.

So did you check the new build in the meantime?