I've been having the same exact issue for several days now. I've only had comcast service for a few weeks now and this is the second time i've had this problem. The first time I went to the local comcast office and the problem was resolved, but now it's back. I tried calling support, the first time my call was disconnected. The second call the tech said that he would try refreshing my account and that it might take a half hour or so if it works and that he would call me back in an about an hour so see if it was fixed. It didn't work and he never called me back, very frustrating.
If you find a fix or workaround for this, would you please let me know as well?