"Age of Empires II scrolling gets stuck after Alt-Tab away and back" ( http://bugs.winehq.org/show_bug.cgi?id=30814 ) has been debugged now.
The problem is that GetKeyboardState starts returning 0x40 after changing window. Documentation seems to only define LSB and MSB ( http://msdn.microsoft.com/en-us/library/windows/desktop/ms646299(v=vs.85).as... ). This leads Age of Empires II to believe that all keys are pressed after changing window, making it scroll unstoppably.
Should this be fixed by removing extra bits in GetKeyboardState like in the bugzilla entry, or should it be fixed in wineserver? Also does the similar functions GetAsyncKeyboardState() and GetKeyState() need fixing?
Another (minor) problem raised in the bugzilla entry is that, if a key is pressed when changing window, and released before returning, GetKeyboardState() will claim the key is still pressed (0x80). But this is easy to workaround, just hit the key again inside the game and it will stop scrolling.