Same issue here but with only one of my email accounts. It would be nice if for once Comcast talked to us about the issue at hand and provide an estimate of when it will be resolved. I know that technology issues occur. All I want is a customer service ethos that thinks of the customers and their concerns.
We have 3 comcast email accounts. We are using 3 separate Thunderbird portable programs. One email address seems to experience more difficulty connecting (when the "get mail" button is pushed) than the other two. It seems to take forever sometimes but it does eventually connect. Now, before anyone asks, all 3 are provisioned exactly the same way and connect over the same network, from the same PC. This tells me the problem has to be downstream.