The problems Vegas has with mpeg2 is about the container formats usually. For example, .vob files usually slip on A/V synch, but if you re-wrap the mpeg2 format from these files into an .mpg container, or even better, a .mod, .tod, or .m2t container, there's a good chance it will work better. Container's job is to work as a buffer for such things between the editor and the actual format.