I just realized that the prerender bug is still present in 8.0c. After just a few prerenders to 1080i MPEG2 to preview color and level adjustments, now it shows the prerender progress, but when it's done, no blue bars, and no playback from the prerendered files. The only way to get back to normal is to close Vegas and reopen it, wasting time waiting for the project to load.
So Sony, how many people did you have testing this thing? Just one high schooler one or two hours a day, right? Heck, I would've caught it even if I had tested it that much.