I have the same problem. I upgraded my old site to 2.3.
Now It says:
ERROR: WordPress requires Cookies but your browser does not support them or they are blocked.
ERROR: The username field is empty.
ERROR: The password field is empty.
BUT… The only difference is that whatever it says, I can log in to the admin panel or register a new account without any problem. Im using a Mac OSX Powerbook G4
Blessings!!
