I was using Ebay.co.uk normally and could see saved searches, my watch list, my messages and search the site. When I tried to sell an item, the Ebay page came up for me to enter my username and password. It ignored this and came up with the same login screen. Tried many times. I closed the tab and then went into the Ebay site again. It accepted my username and password provided I was only using certain pages (saved lists, messages, search. etc.) but would not accept my login to sell an item or revise an item currently on sale. I phoned Ebay customer support. They suggested that I tried Internet Explorer and "reset" Firefox. Internet Explorer worked. I deleted the cache and cookies from Firefox and restarted Firefox. Everything started working again, but a few days later exactly the same thing happened (and I fixed again by deleting cookies and cache). It seems odd the Ebay will allow me to login for certain activities on their site, but not others.