Mabey a bad cable modem

I have been having problems keeping an Internet connection. Starting yesterday I have only been able to be online for about 4 minutes, then I get the generic" cannot find server" message from windows when I try to navigate to another page or open a new explorer window. If I unplug my cable modem for a few minutes, then plug it back in I can get on the Internet for another 3-4 minutes. The only other person in my neighborhood that has cable Internet isn't home so I can't ask anybody if they are having the same problem. I think maybe my cable modem is going bad.I have run norton anti virus(negative), spybot search and destroy( said it found coolsearch, deleted,run again negative). I used go-back to revert my drive back to when I had a good connection. and I have looked in the windows task manager and the only process I can see thats not normally there is msmsgs.exe, which is some kind of messenger process( i don't run messenger, so I shut it down). can anybody help or give suggestions.
specs
amd 3000 64bit
geforce 6600gt pci express
asus a 8n-e mother board
2 gigs pc3200 corsair valuram
modem is moterola sb4200 surfboard
windows xp home sp2

 

AN update: If I go to network connections , it shows my connection is good even when I cant get the internet. If I "repair connection", even though it shows a good connection , I get the internet back. Any Idea why this is happening over and over.

 

My first question is have you called your isp to troubleshoot the issue? As much as I hate to recommend this to anyone, its the best solution as they are trained to support your equipment and would have the best idea if they area having any issues in your area.

 

I hav'nt called them yet. My pride usaully keeps me from doing that till all hope of fixing it on my own is lost. but mabey now is the time.