Ok, that's a separate issue. So let's clean the slate.

1. Make sure you've recompiled package.el, and restart Emacs.

2. Turn on debug-on-error with M-x toggle-debug-on-error

3. List packages, wait for the refresh to finish, then try to `U x'.

4. Do you get an error buffer? And what messages do you get in *Messages*?

Thanks