Changing mux-rate

When i cut a mpg the mux-rate (I don't know exactly what it is) changes. Normally not a problem, but in WinOnCd 5 it is. It has to decode everything again, which costs a lot of time. I cut the movie with TMPGenc. If I want to make a CD of the original movie (oncut) there is no problem with the mux-rate.
Who can help me out, or knows a site where this problem is explained?
Thanx in advance.:cool:

The Iron One
 
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