http://bugs.winehq.org/show_bug.cgi?id=10142
--- Comment #26 from David Taylor davidt-wine@yadt.co.uk 2008-09-29 01:43:10 --- I'm not entirely sure if it matters if it happens on other WMs -- to me the behavior shown in the logs is clearly broken.
In any case, I installed fvwm2 v2.5 and tested it there. I see exactly the same behavior: without the patch the window disappears if I set the window to 'not on top' when it off screen; and with the patch it behaves as I would expect.