This sounds like a DHCP lease “problem.” I put that in quotes because this behavior is designed, to some degree.
Most home internet connections are set up to use DHCP, which means only that it gets its IP address from a central DHCP server. When you start the computer, it “checks out” a DHCP lease that contains several pieces of important information. The most important pieces, of course, are the IP address, the default gateway (router), the subnet mask, and the DNS server.
The thing probably causing your problem is another important piece of DHCP information… the lease. If the duration is, say, 12 hours, your computer knows that it cannot use the lease for more than 12 hours without “checking in” with the DHCP server. From the server’s side, if a DHCP client doesn’t “check in” after 12 hours, it revokes the license and grants it to another client. So your computer is going to sleep, the lease duration is being exceeded, and the server is giving your address to someone else. You can’t get back into the network until you reset your computer, which causes it to “check out” another address.
The next time this happens, you can positively test to see if it is a DHCP problem. Instead of resetting your computer, open up a command window and type the command:
ipconfig /renew
If all goes well, you should see your new IP address, subnet mask, and default gateway (and of course your network should start working again).
Try that and let us know how it went.
If DHCP is the problem, the first thing you could do is talk to Comcast and ask if the lease duration was set too short. That happens sometimes. If they reply negatively, the next thing you need to work on is your computer’s own settings regarding how it goes to sleep and wakes up. You can change settings on your computer to allow the network connection to wake up the computer to do things like this.
What is the reason for DHCP? 2 reasons… first, if the network changes in some way, DHCP guarantees that you will check in at some point and pick up the changes. Second, IP addresses are a limited commodity. Internet providers know that no more than 1/3rd of users are actually logged in at any time, therefore DHCP allows more effective allocation of IP addresses depending on who is actually logged in.
Hope this helps…