Spyware always has the possibility of keeping you from getting on the Internet. What if the spyware is affecting DNS, and the person doesn't know to try and ping the IP of a Website, instead of the name? So it's possible (although not with this issue). Troubleshooting over the phone usually doesn't work with these types of issues- simply because if the rep does fix the problem, it's outside of what Comcast supports. I don't think the splitter is the problem, its the SNR (signal to noise ratio) that is causing the problem. If the signal is not strong enough, you're tv can work fine, and the modem will seem like it's connected, but won't connect. They will be able to see the signal levels when this user calls in. If you disconnect the TV from the splitter, and the Internet works, you probably will need an amplifier installed on the line- at your cost unfortunately.
