So, to want to do this you must be editing on a PC then Authoring on a MAC, right?
Do you have a network connection, external, or removable hard drive so you can mover your edited files?
If you are going from a PC to a MAC you must render from VEGAS as an MPEG 2 (DVD format) or MOV (QuickTime/MAC format).
You may want to check how DVD Studio Pro handles the streams coming into it. You may save yourself another render in DVD Studio Pro by rendering from VEGAS in the correct format. Also you may want to compare the quality of the codecs and find the best way with the least degradation.
Quicktime doesn't work so well in DVD Studio. Just was messing with this yesterday. There are too many variables, and DVD Studio can easily get confused. Separate streams of AC3 and m2v are what is easiest to use.
Odd, to be discussing Apple tools in the Vegas forum, eh? :-)