http://bugs.winehq.org/show_bug.cgi?id=9452
--- Comment #7 from Joan Coll Cerdán johan_az@hotmail.com 2007-12-14 14:17:23 --- I can confirm that deleting the ClientRegistry.blob from the Steam folder and letting it to update again, solved the problem.
I wouldn't say that this is an invalid bug, since it doesn't happen in a real Windows environment (as far as I know).