http://bugs.winehq.org/show_bug.cgi?id=2908
------- Additional Comments From mike@navi.cx 2005-27-04 18:36 ------- I expect this is because X11 windows are only used for toplevels now. If so then it was a known and expected regression. Try asking on wine-devel about it.
If it's because of the WM rewrite then it won't be easy to fix. New X server features will be needed.