http://bugs.winehq.org/show_bug.cgi?id=15551
--- Comment #19 from Vitaliy Margolen vitaliy@kievinfo.com 2008-10-13 09:09:02 --- I'm more asking what prompted you to use UserIosb if you don't know what's it for?
Anyway, I think the correct fix is to set it to NULL. Because the APC that it should be used in (ioctl_completion) works different in Wine and gets it's result from the server.