I think I know what the issue is. The good news is that we have the solution - the bad news is that you'll have to contact Vimeo first.
Brief history. Vimeo is upgrading their API from v2 to v3. They seem to be slowly removing v2-related pages from their site, so you can't see the "OAuth" tab. We have written the code for TubePress to work with v3, but it's not quite production ready. Point is that in the future you won't hit this problem.
Here is the thread with the other customer that had your exact issue. The last two or three posts are the relevant ones. You can contact Vimeo using the form here - just click the "Still need help? Contact us." link and send in your message there. You could even send them a link to the other thread here to refresh their memory. They seem to be pretty responsive with this stuff.
Give that a try?
Thanks!