OK, so the same thing happened to me today. Was using Chrome. The thing you may not have noticed is that it was redirecting to a site other than paypal.com. Don't recall which one. Anywho, I went ahead and used a different machine to then change my password on ebay and paypal as well. Why? Because this smacks of browser virus or something hackalicious of the sort.
Some background which may or may not relate: I recently had installed Java and it subsequently installed the dreaded Ask toolbar. Ask was not in the list of programs I could deinstall so I had previously disabled it in the add-ons. But since this weird Paypal issue arose, I decided to uninstall Chrome, then reinstall it. Then in Advanced Internet Options, I hit reset, and checked Delete Personal Settings, then clicked Reset. I had to add my Favorites toolbar back to see my favorites were intact after a momentary freak that I might have lost all my favorites. Anyway, my browsing's much faster and I was able to pay from ebay using paypal from IE browser. All is well now.
