Dunno if this will solve your problem or not, but;
You are probably getting a conflict between drivers due to that Pinnacle converter box (if I understood your post correctly). I don’t think Vegas works all that well with Pinnacle. I have Studio 9 on my system and the internal AV/DV board with the BlueBox, and it’s going as soon as I get a chance to open the case and pull it; I don’t dare use it with Vegas.
I’ve already got a Canopus 110 to replace it (external, but hey, whatever), and that will be my AV/DV converter from then on.
Of course, I usually export through DVD Architect 3 to a DVD, instead of burning tape, but I know at some point I’ll be exporting, as well as importing to 8mm or VHS – both on a GoVideo deck.
Good luck, and I hope you cure your problem.
Jim