My login also was the same starting in about Jan
I'm not very knowledgeable of computer issues.
I noticed the TW login problem also on my other computer. It started about the same time as my AVG was finding viruses on that computer (not in use and still very suspect). I also learned that some months previously Windows Automatic Updates had stopped.
There was another familiar site which if I went to it by some regular bookmarked links would look normal. If I went to it by one particular bookmarked link, however, there was delay, the font changed and some unusual numbers appeared across the top of the screen. I could no longer REPLY with normal text.
I still don't know what if anything happened to my other computer, stopped using it in early Feb.
1) Check you last Windows Updates
2) Do a virus scan.
3) Look at the complete history of your virus scanner and see if it has been finding anything. What is in the vault?
Login seems to be OK on this second computer.
The computer security situation in 2012 for the average user is completely unacceptable.