http://bugs.winehq.org/show_bug.cgi?id=30637
--- Comment #1 from Alen Siljak alen.siljak@gmail.com 2012-05-10 06:43:33 CDT --- Running on a clean prefix completes the installation. So the error must come from one of the commands ran prior to dotnet20 installation:
./winetricks fontfix ./winetricks corefonts vcrun6 ./winetricks gdiplus
Will check in details.