BarZaTTacKS:
Since I have no idea of your setup i.e. operating system, browser, router, modem or connection (wired or wireless) etc it's really hard to comment but you have to realize that while this problem could well be a Comcast issue it could also be any number of other problems as well i.e. malware / a virus on your system, a problem with your modem or router or even a signal strength problem on your line.
You try and make a point that if you stream the same show to two computers on your network at the same time and they both stall at the same time it's got to be Comcast's fault but that's not necessarily the case. If your modem or router is failing or overheating (check the top and bottom of both and see if they feel unusually warm) then it could well be your equipment and not Comcast or if you have low signal strength on your line that could also cause a problem.
You're going to have to do some trouble shooting, like if you have a separate modem and router try bypassing the router and plugging one computer directly into the modem and see if you're still having a problem. (Just remember to powercycle the modem when you plug the computer directly into it.
- Norm