http://bugs.winehq.org/show_bug.cgi?id=24349
--- Comment #5 from Austin English austinenglish@gmail.com 2010-09-12 14:02:06 CDT --- (In reply to comment #4)
Although useful to get rid of Mono-related default registry keys it only has to be done once - after clean WINEPREFIX, not in-between .NET 2.0 and 3.0 install (2.0 is prerequisite).
File a bug with winetricks.
Fixed in winetricks svn. Thanks.