It's happened to me before. Only with some video, not all of it though. It really pisses me off. I love Vegas, but sometimes it just refuses to work with me. Good luck man. Let me know if you figure it out.
RIP Shane & CRJ
"It's fucking Halloween, who cares. People either get drunk, or go into a sugar induced coma. Basically, everyone passes the fuck out" - Mr.Panda
I have had the same problems with some avi files. If you convert them to something else they'll work. Right now I convert all my mp4 (h264) to m2ts (?) HDV format. There is a loss in quality but its so much easier to edit as h264 is so compressed its hard to edit. Also if I try and convert it lossless avi etc the file size is just huge and I dont have the space. I think m2ts (mpeg) is a happy medium for me for now.