Some WMV files won't play, some play jerky

I’m having a problem with Media Player (0.7.0 - I’ve seen mention of 0.7.1 in the forums, but my version says 0.7.0 and there’s no update available), where some .WMV files cause the ATV to reboot. Others give me a warning that playback may be stuttery or jerky (I can’t remember the exact wording of the warning), and they are. All these files play fine with VLC on my Macbook. Any ideas?

The current version of Media Player is 0.8-144748. If you have the latest version then this is the number that is displayed when you go to Maintenance->Manage Extras and then cursor down until Media Player is highlighted.