Windows 7 - Media center 'jump' unresponsive but media player fine

Hi everyone,
I'm having trouble with MCE being unresponsive to user input.

I have an AVI file ,(properties are listed below,) which plays back fautlessly in media player but media center seems unresponsive to user input during playback. In particular it is nearly impossible to be able to jump from one point in a video to another.

This seems odd to me as I would have thought they would both run the same decoders under the hood.

Any help would be much appreciated,

Cheers,
Si

frame width 512
frame height 384
data rate 577kbps
total bit rate 769 kbps
frame rate 29 frames/second

audio
192 kbps
stereo
48khz

just a quick update. My cpu usage is shown by the cpu monitor gadget to be 100% during playback of the file in both MCE and Mediaplayer. Despite this I can use my pc whilst playing the video in Media player. I'm running it with word and firefox open at the moment.
Cheers,
Si