http://bugs.winehq.org/show_bug.cgi?id=27650
--- Comment #22 from Jamie Anderson jamie+winebugz@jamieanderson.org 2011-11-30 18:45:34 CST --- I had the same problem as Comment #21 with the bad torrent file error.
If you haven't installed any IE Winetricks, you can close the WoW Error dialog when Launcher.exe crashes and get into the Downloader Preferences and make the necessary changes described in Comment #16. I don't think this works if you have installed any version of IE however, because you then get a different error popup.
By the way, the workaround I suggested in Comment #15 does not work, don't try it.