When I open an MKV file in AVSPmod, it will display some of it mostly in black with some colored blocks of the footage showing. I currently have CCCP - some forums I found mentioned using ffdshow, but that didn't work. I also tried updating the ffms.dll and .avs files as recommended by another forum post to someone who was having the same issue, but that didn't work either.
In regards to avi files, I get the error "avisource couldn't locate a decompressor for fourcc".
In both instances, I've been able to open these types of files in the past with no issue, but I the only thing I can remember that changed was I strictly went with CCCP instead of other codec packs and other codecs (hence why I tried reinstalling ffdshow again to see if it might help).
Gspot has listed that the required codec for the avi is installed, but it won't display any information regarding the mkv.