This has been discussed before, most recently on wine-users, I think... Are you running in managed mode? Then try this patch: http://www.winehq.com/hypermail/wine-patches/2001/11/0126.html
(Hey, Alexandre, is there a reason you haven't applied that yet, anyway?)
I applied the patch succesfuly, but it doesn't help, either in managed or non-managed mode. The message box still pops up for a second and then disappears.
I was wondering why message boxes are allowed to be APPLMODAL, TASKMODAL and SYSTEMMODAL, while other dialog boxes aren't. I feel it would have been simpler and cleaner to implement TASK/SYSTEM/APPL modality in windows/dialog.c instead of windows/msgbox.c, as dialog.c already disables the root ancestor of the dialog parent.
I still haven't found out how to increase the extra memory of the MSGBOX class. Any info will be appreciated.
Laurent Pinchart