The beta testers did see this problem as well. It is in our list of issues to address.
is there an ETA for when this is gonna get fixed? I would understand if the latest update was just a patch, but you released a new product with core features missing and beta testers even told you about it..
I wouldn't say that core features are missing, because the render to new track still works. It's just that a few popular codecs for rendering to a new track are not accessible at the moment.
When all bugs should be fixed before releasing a new Vegas version, then we would probably wait forever to get a new Vegas version.
I'm sure that this bug will be fixed in a next coming update, for that time use one of the other available codecs for rendering to a new track. Or when rendering to new track is just for preview purpose, try selectively prerender.