bogus extra RET required when entering filenames (etc)?

[Miles Bader]

There's a file in /tmp called "/tmp/x.c".  I type:

   C-x C-f /tmp/x.c RET

However, instead of visiting the file (which incidentally is already in
a buffer), emacs prints " [confirm]" at the end of the prompt, and I
have to hit RET again.

This didn't happen with an emacs from ~2 days ago, so it seems to be a
new problem.

Thanks,

-Miles

-- 
The car has become... an article of dress without which we feel uncertain,
unclad, and incomplete.  [Marshall McLuhan, Understanding Media, 1964]