I'm getting this same problem, and I do have cookies enabled. I was on earlier today and I logged in fine, but when I came back I was no longer logged in. Now when I login it doesnt seem to be reading the cookie at all, because as soon as I go to another page I am no longer logged in.
I just tried deleting the cookies and logging in again, and it never set a new cookie and I had the same problem.
EDIT: nevermind. It turned out to be the protozilla plugin I installed for mozilla, so that it would send ed2k links to xMule. I uninstalled it and cookies work again.
