There is a regression in wine 0.9.4 that caused many programs (between them, if you want to check, Firefox and Thunderbird windows installers) to crash. This issue has been reported in wine bugzilla (see for example: http://bugs.winehq.org/show_bug.cgi?id=4147) and there is a fix on a wine mailing list: http://www.winehq.org/pipermail/wine-patches/2005-December/023021.html I tried that patch and it fixed my problems; I'm not sure if it has been applied to wine tree, but I think that this bug report here could be useful to other users.
Created attachment 75495 [details, diff] patch for msvcrt regression in wine 0.9.4
in portage, thanks
*** Bug 116736 has been marked as a duplicate of this bug. ***