Video Sticks at Transition point rendering
 

I shot some vacation video with my SR12 and HMC150, edited in timeline and came up with about 14 mins of video. Sometimes, near the end of the time line, while previewing, the video would "stick" at a transition point of one clip. The audio continues on its merry way, but the video shutters and acts as if it is in a millisecond loop. I removed suspected problem files completely, replaced (or sometimes just left out) and the problem would occur in other place, almost always near end of project but at no common point on timeline. Closed and reopened Vegas 8.0 (and upgraded 8.1) watched entire project run smoothly but same problem would reoccur during the render process (both .mov and wmv).
I have a new quad core Dell, have tried this with and without "multicam editing" enabled, basic overlap transitions and a few clips slowed down for slo-mo.
Just wondering if there is something basic that I am missing or possible suggestions for trouble shooting.

Thanks in advance,
Doug

I had a clip near the end that had been slowed down (slo-mo) which I changed back to normal rate and my problem went away.