BibTeX and url

If you ever run into this:

(./foo.bbl
./foo.bbl:12: Undefined control sequence.
 \Hy@pstringURI 

l.12 ...refix\url{\url{http://tsunanet.net}}

./foo.bbl:12: Undefined control sequence.
\hyper@linkurl ...Action/S/URI/URI(\Hy@pstringURI 
                                                  )>>}\relax \Hy@colorlink \...
l.12 ...refix\url{\url{http://tsunanet.net}}

./foo.bbl:12: Undefined control sequence.
\Url Error ->\url used in a moving argument. 

l.12 ...refix\url{\url{http://tsunanet.net}}

and, just like me, you go like "WTF, I did \usepackage{url}?!". The answer is to NOT use \url in the URL field... The link will be created automatically anyway.