http://bugs.winehq.org/show_bug.cgi?id=26997
--- Comment #6 from David Finch david@mytsoftware.com 2011-05-13 21:48:14 CDT --- That seems to fix this issue.
There is a new, probably unrelated issue where the Steam (or at least its tray icon, not sure about the rest) is now unresponsive after Fallout:NV exits though.