Hi gamma,
If you ask me it sounds like a muxing problem

.
Or maybe a SAP issue with the media in hands/recording speed?
I am no expert when it comes to DVDLab but I've heard there was a muxing problem with it.
Can you check for the latest DVDLab release which should be 1.4x?
The muxing problem seems to have been solved in that release...
Also is there a way to specify the vbv buffer in DVDLab?
If so try to keep it at 112KB.
Others like Phil or Incredible, more used to DVDLab and more experienced in the video encoding issues, may
have more options.
So stay tunned

Cheers