Upgraded to Quad core. System exception Access Violation

[rs008f]

I upgraded my CPU from dual core to quad core and I got this error message, the exact AVS script was working fine on a dual core CPU.

DirectshowSource("C:\ABC.MKV")
gives this error
Evaluate: System exception - Access Violation

This error does not occur on AVI or MP4files, just MKV.

I have the latest Avisynth 2.5.8

[rs008f]

I found out this only happens if the MKV contains AAC or OGG but MP3 works fine.

[rs008f]

Uninstalled Community Codec Pack and installed ffdshow and Haali Media Splitter, now it works fine. Looks like it's the codec pack that's the problem.