http://bugs.winehq.org/show_bug.cgi?id=9579
--- Comment #9 from Dmitry Timoshkov dmitry@codeweavers.com 2007-09-07 09:00:41 --- Certainly in Win32 focus can be set to a not visible window, and in Wine we have tests for that. I don't think that this spurious X_SetInputFocus error has anything to do with real problem.
What video drivers do you have installed? Did you try to run under other window manager?