I had problems using the web admin 127.0.0.1:631/printers. I was able to get to it but could not add or configure anything. I read after doing the fix below that if you log on as root (need to enable it) everything should work regardless, but didn't try it.

Anyway, the fix I found was modifying the authorizations in /private/etc/cups/cupsd.conf. My problem was in the <Limit GET> section. The file is pretty self-explanatory as how to configure authorizations (type and class). In my case I made it authtype none, and authclass anonymous and it seemed to do the trick. Don't know if I've greated a huge security hole, but you can always do the updating in the server and put limitation in.
Here is the CUPS manual has more details on configuring: http://www.cups.org/sam.html

Thanks for this tip - it worked for me!

Tim