Hi,
I have had a similar problem just recently although whilst working with Final Cut, anytime the camera moved or there was sharp movement on screen these lines would appear. The problem I had was with the file type, can I ask if the files you are using, are they the original files or did you convert them into a different format to use in Sony Vegas?
I recently took some footage from my camera which was in a .mod format which was incompatible with Final Cut so I converted it to MP4 which worked but had these same lines as you have, I found instead that if I converted it to a DV format the lines would not occur.
I converted them using ffmpeg video converter, although I have used Sony Vegas in the past I don’t know if it is compatible with .dv files or similarly which filetype you should have converted your file into.
I’m sorry I can’t help you any more but hopefully I may have put you on the right track.
Regards
Daniel