This is very strange...ever since I had the cable modem and service installed about a year ago, the computer will not boot up unless it's been off for atleast one hour. If I wait less than an hour, or do a quick ctrl+alt+delete reboot, the computer won't make it far past the windows login because it freezes. Anyone ever heard of this problem?

I can tell you that it's a hardware problem. Try reseating all the connectors in the box. It's best to do it one at a time.

This sounds like it could be a heat problem to me. Was it an internal cable modem? I have trouble with my computer overheating because I have alot of add-in cards now. I have to keep an external regular house fan blowing at it or after a short time an alarm will sound (my mobo has a built in heat sensor and alarm). Then I have to shut it down and let it cool. I have added internal fans, but it still over heats. Believe it or not the small regular house fan does the trick. Could it be possible that your mother board is overheating? I think that could cause it to not re-boot until it cools. Are you experiencing alot of freezes or other "odd" behavior?