TMPGEnc dvd author is on sync on one computer, off sync on another

i don't know why. it work right on the worse comp

on my computer (gateway 2.2 gig 512 ram XP 80 gig) the a/v is off after i author some mpeg video (Root5)

i author 2 mpeg file (roots 3 and 4)on my wife comp (XP 70 gig 256 ram amd 1200) and the a/v sync is fine

any idea why? this was the first time i use it