There are a number of Common viruses that cause login loops, like the one you are explaining. try running the free version of Super Anti Spyware, as well as ESET Online Scanner (Both are 100% free). I deal with problems like these on a daily basis, as I work servicing computers. IE 10 has also had many issues with Ebay, Outlook.com, as well as multiple other sites. If you have IE10 you can downgrade to IE9, which should resolve the problems if it was not a virus.