In Vegas 11, I noticed that the entire list of render formats disappeared with a cryptic "No matching formats found" message. Per other posts, I uninstalled and re-installed Vegas 11 build 701. No joy. I loaded a different project, and shazam, there was the entire list of render formats. But back to the original project, no render formats. I was able to correct the missing list by deleting everything from the timeline. When I put things back on the timeline, the full list of render formats was once again present. So, I conclude that there was something on the timeline (which had since been removed) that caused the "No matching formats". I suspect that it might have been a full HD (1920x1080) track in addition to a HDV (1440x1080)track. Not a very friendly solution, but perhaps useful to someone.