Can you change how much of the systems ram the on board graphics is using. You might raise it if possible and see if it is a buffering issue. Also if you rewind a second or two and replay the bad spot does it get past that bad spot and lock up later.
The fact that you said something about it playing in VLC and not in MCE makes me think it is a codec issue. But I have never had to deal with codecs since using WMC.
Sometimes AVS forums has threads dedicated to a single motherboard and you might find answers there.
Have you moved up the list for the CETON tuner yet?
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