Sounds like a real pain :-(

one thing that was mentioned that you may or may not have picked up on. at the top and in the address bar is NEEDs to say that you are logged in. sounds like that is the problem you need to fix. the cookies / redirects thing.

a couple things to try....
make sure your time is set correctly on your computer.
make a new user profile on your computer so everything is fresh and just do this one thing.