This happened to me once, and I know of at least one other case as well. Both times, I, and the other person plagued with the problem found resolution by flushing their cookies.

We also were both using Internet Explorer. Apparently somehow one of the cookies used in maintaining state for this site was somehow either corrupted or misunderstood by IE. Go into your Tools menu, open the Internet Options dialogue, go to the General tab, click the Delete Cookies button. Click OK. Close Internet Explorer. Restart Internet Explorer. At that point, you should find the problem to have been resolved (hopefully).

Reminds me of an old joke I've heard told several ways. I'll tell it my way:

There were three engineers riding in a car; a chemical engineer, a mechanical engineer, and a Microsoft Sofware Engineer. As it goes in jokes, the car broke down.

Immediately the mechanical engineer said, "Don't worry, I know what to do. We need to adjust the timing, and tighten the belts. We'll be back on the road in no time." ...but after tinkering for a few minutes, he was unsuccessful.

Disgusted, the chemical engineer snidely chimed in: "You're nuts, the real problem is in the fuel-air mixture. I'll adjust the carburrator, clean out the air-filter, and we'll be back on the road in a jiffy." ...but after tinkering for a few more minutes, he too was unsuccessful.

By this time the Microsoft Software Engineer was beaming with pride, and could hardly contain himself. "I've seen this all the time. I know what we need to do to fix it.", he said. "We must close all the windows, shut it down, restart it, and then open all the windows again." Amazingly, they were back on the road in no time.