Well, finally something that I have experience fixing (I used to fix comcast internet issues at a call center for a living)... but from the sounds of things, it looks like you've done the right thing by calling their tech support.
Got to ask a few questions though:
Do you use a Router?
If you do, have you tried hooking your computer directly to your modem?
If you have done that, do you still get the same issue?
When this issue happens, (And I'm asking this assuming you're using a Motorolla SURFboard Modem, like the SB5102, this is the modem I have at home) What lights are flashing on the modem? Normal activity has 4 solid green lights, and a flashing orange activity light.
What operating system do you use and are the drivers for your network card up to date? (if you're a Comcast Customer, the minimum OS you should have is WinXP SP3 or OSX 10.5 or 10.6, this may have changed since the last time I've done this kind of work)
Now, if it is packet loss, there could be any number of reasons:
The cable infrastructure in your area may be lousy (very likely, the one in the service area I was in was, the Greater Chicago Area), Comcast are very cheap MoFo's, and your cable in your neighbourhood may be 10-25 years old, or more.
The Levels for the signal being sent to your house may be too high (over powering the modem, causing it to reset), or too low (causing the modem to lose connection, causing it to reset).
Your modem may be faulty.
Answer these questions and I can help you further, but eventually, you're going to have to phone them to get it fixed, regardless of the help you get from me, because this sounds like a hardware issue on Comcasts End.
If this is an issue with Comcast, you're going to have to prove that it is to get any help out of them, and to do that, you have to eliminate your computer from the issue, here's how you do that:
- If you have more then one computer in the house, try and replicate the issue on that computer.
- Make sure your computers OS and all network drivers are up to date.
- Make sure your computers virus scanners and firewalls are either properly configured or disabled, and try and replicate the issue.
- The next time this happens, try power cycling your modem. To do that, make sure your computer isn't making any requests form the internet, like downloading or anything of that nature and follow these steps:
Once you do that, wait to see if the issue happens again
- Unplug your modem's power supply
- Wait 5-10 seconds
- Plug the modem back in and wait for all 4 green lights to turn solid green.
If you've done all that, the issue's with Comcast.
When they do come to fix the issue, it most likely involve a Tech coming out and adjusting the levels being sent to your house, and/or replacing your modem if need be.