Hi -
I'm getting the same issue after having upgraded to Win7 and PL/SQL Dev 10. Some other things I've noticed:
1. If you alt+tab past the second PL/SQL Window and alt+shift+tab back to it, the problem does not occur.
2. If you alt+tab all the way around your window list and then to the second PL/SQL Dev window, the problem does not occur.
3. It doesn't seem to matter how slow or fast I do alt+tab - if I go direct between two PL/SQL Dev windows, the problem occurs
4. Since the window you're trying to switch to has focus, just isn't on top, you can use alt+space to open the window control menu and restore/maximize the window to get it to the front.
All of those are really annoying workarounds. Hoping there's a solution in the works for this.
Thanks.