Cannot play MP4/DIVX/MKV files with WMP

I am on Win7 Ultimate Retail x64. Before discovering DivX Plus for Windows, I had files working in WMP via a simple combination of FFDShow, and Haali Splitter. I uninstalled those with the included uninstall executables, and installed the DivX Plus for windows. My MKV files will play with the DivX Player, but NOT with WMP or WMC. The entire purpose of this is to stream to my 360.

How do I get MKVs and other DivX files to play in WMP? Is there something interfering with MKV playback on my machine? Are there residual artifacts from my previous FFDShow/Haali installation?

I haven't installed a codec pack, and rather installed individual pieces.

Lapse...

Sorry, I haven't held up my end to get help. I DID install the AC3filter, and it didn't fix the issue. I'll install mediainfo soon and analyze some of my sample files and post the results here.

MediaInfo

Can you run MediaInfo on a couple of the files and post the info here so we know what kind of files are giving you trouble?

Also, did you install AC3filter? This seems to help, since many MKV videos use different audio formats and for some reason this can cause blank video screens.