ruserious - 9:09 am on Jul 11, 2004 (gmt 0)
I think these problems may have something to do with having different Google-Accounts. I never had Problems logging into Adsense for the first couple month.
This suddenly changed when I got a gmail account. I was having the same problems.
Now I use different Browsers for the different Accounts and everything is fine. I suspect it is somehow relatd to the cookies (clearing them and reloading the page remedies the problem too).