http://bugs.winehq.org/show_bug.cgi?id=30707
--- Comment #11 from Anastasius Focht focht@gmx.net 2012-05-26 02:07:13 CDT --- Hello Austin,
the most important part missing: the installer has to be run with fusion set to "prefer builtin". If this temp override is not set the GAC remains empty after install.
--- snip --- WINEDLLOVERRIDES="fusion=b" $WINE dotNetFx40_Full_x86_x64.exe ... --- snip ---
Regards