Many customers are having this issue. It has been reported to Comcast multiple times. Here is one way you can try. This was suggested by a customer today and worked for him.
Go to to comcast.com
Clicked on "My Account" at top of page
Clicked on "Sign In" (Sign in fails)
Clicked on "My Services"
Clicked on "Sign In" again (Sign in fails - again)
Clicked on "My Account" at top of page (I'm in)
Need Email Help? Please post the following information in your post. Do you use XfinityConnect? The Full or Lite version? Do you use an email client? Which one? (Eg; Windows Live mail, Outlook, a smartphone etc.) Which browser/version do you use? And- have you cleared your browser cache? Which operating system? XP, Vista, Windows 7, Mac OS X Details of the problem you are having.
Hi there. This was a known issue that our engineers were able to resolve last night. I'm sorry for the trouble but you should be able to log in now. If you are still redirected, please try clearing your cache/cookies/browser history and log in again. If you have futher questions or concerns, feel free to email our team at We_Can_Help@comcast.com. We would be happy to help.