I had some 8mm film transferred for a client when I got it back from the transfer house I noticed a moiré like pattern on the transfer, does Vegas Pro have any filter that will remove or lessen the affects of this.
Is the pattern on all the film or is it specific to certain sections? I've transferred many miles of 8mm and I've never seen anything like you describe.
Are the lines exactly vertical? If so, perhaps the film is Polavision, Polaroid's instant film. I am at this very moment transferring nine cassettes of Polavision and it has some very nasty lines that result from how the instant emulsion is formed:
A very light horizontal Gaussian blur (about 0.003) removes the artifact, although I am working on a possible better solution.
If you can post a few seconds of your capture, I'll have a look at it.