While you're waiting for Comcast, check your HOSTS file. Lots of malware will modify it. It's found in C:\windows\system32\drivers\etc folder on most Windows versions. It is a text file you can open with Notepad or Wordpad. It should have a single entry, "127.0.01 localhost", and possibly many lines above this that begin with "#" - these are comments.

If your HOSTS file has been modified, delete the garbage lines, save it, and reboot.