Media Browser - file cannot be found error when trying to play MKV files

Here is the solution to the problem I found:
1) Install this Divx Codec Plus pack
2) Install AC3Filter

Now my MKV files play and I can hear them. Without the AC3Filter I had no audio. I am getting choppy playback though so I don't know where to point the finger for that problem. Is it my network or is it a codec issue?