Live TV is pretty resource heavy, if you have any viruses, spyware, adware, or malware then you 'll frequently see stuttering and crashing. Acidforum is also on the money that any outside CODECs can cause issues.

Troubleshooting 101, what's happened between when it worked and when it now doesn't', what was installed?

Diane

http://support.microsoft.com/kb/929833
try this,

i have only once had a problem with Media Center and that was down to a corupt registry which needed repairing(problem was on another computer not the touchsmart)..

But like Diane said,
if media center was running fine before and this problem has only just come up determined what programs were installed???
you could try a system restore and jump back a few days to when you know 100% it was running perfectly...