Try running C:\Windows\Microsoft.NET\Framework\v4.0.30319\ngen.exe update
that is 32-bit, there is also 64-bit:
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\ngen.exe update
Same applies for C:\Windows\Microsoft.NET\Framework*\v2.0.50727, if the first one doesn't trigger v2 cache rebuild.