Can't sign into Microsoft account

[WPCentral Question]

I did the latest update on my windows phone (Nokia 520) but now wish I hadn't bothered. I can no longer upload photos to Facebook or update any apps or upload my games progress to the cloud because every time I try to do so it asks me to enter my Microsoft account password. It gives my username as "< email removed by moderator>@live.com which it has never been to my knowledge (my username is my email address). I can't find out how to change my username when I am online, and when I try to enter my password on my phone it does not accept it. There is no option on the phone to change the username to the correct one. If anyone can offer some advice as to how I can rectify this, either by undoing the phone update, or to change my username, I'd be grateful! Otherwise I will no longer be able to update apps or upload photos or video using my phone, which is not satisfactory!