Is anyone using this product successfully with Vegas?

I've just started to experiment with it, but when I try to 'add a media asset' (import an MPEG2 file) I get the following error:
"Error in the System Header. Information in its component elementary streams may be corrupted"!

I've just tried a small MPEG2 encoded by Tmpgenc and that worked fine...?

Is there something different about Vegas's encoder, and is there a way to force conformity?

-Pete