Hey
Yes, I also have this buy in Vegas 11 64-bit running on Windows 7. It also appears when I render MainConcept MP4 in 480p. Just like you, it doesn’t show up in the preview or editor window but is there when the file is rendered. I’ve searched the internet high and low but haven’t found a solution. This is one of the places where the problem is even mentioned!
A thread over at the Sony forums suggested that you render at 720p to do away with the green bar, but I have rendering size reasons for rendering at 480p (long interviews to be shared with project group through Dropbox).
Ras