Yahoo log-in page constantly reloads

I don’t know what I did, but the log-in page for Yahoo reloads non-stop. The Yahoo home page is okay but when I hit the log-in button, it starts the reloading thing. It displays a message telling me that my browser refuses to accept a cookie but I have “accept cookies” checked, with the provision that they be kept until they expire. I have Windows XP Home and I’m using Firefox as a browser. The Yahoo log-in process worked perfectly yesterday; this problem came out of the blue today.

This problem does NOT occur when I use IE as my browser.

I’m baffled and would appreciate any suggestions.

Thanks.