Did you encode the file yourself or download it.

The ref frames look ok but it could easily be a bad encode.
I do not have these problems with ANY properly encoded 1080p MKVs.
I have the same movie stutter issue problem with 1080p files. Sometimes also with 720p but much more consistently with 1080p files.
This may seem like a dumb question but how do you encode your own files? Can I download an MKV file that someone has posted and then encode it to make sure that my WDTV will play it properly?