http://bugs.winehq.org/show_bug.cgi?id=23299
--- Comment #8 from Kuro dragon_a.p@gmx.net 2012-07-08 07:12:49 CDT --- Using dcompmgr and openbox here.
Workaround for me: Add "Steam.exe" to Application list and change windows version to 7 Uncheck "Allow the window manager to decorate the windows" for Steam.exe
Btw: With cairo-compmgr and enabled composition Steam windows are not even visible...