Hello guys, I've found a workaround for this bug in windows XP though it may work on windows 7 also, but there's a difference which I'll explain at the end.

Instead of having the Opera windows maximized, choose "restore" and then you resize manually the window to the full size of your monitor except the bottom one, there you leave it half an inch away from it (it can be less than that, try smaller sizes but never full at the bottom 'cause then it won't work).

The issue with windows 7 is that it automatically maximizes a program window when you try to change its shape closer to the size of the display's area, if you can avoid this congratulations then, but I don't have the time right now to experiment on W7, so if one of you try this please let us know if it worked or not.

I hope I've helped to at least one of you.