With Win 7 get Internet access if in safe mode. In standard mode I communicate with router, but not to cable modem.Troubleshooting says device will not accept connection. I get same message if connect with Ethernet directly to cable modem. I used program on Comcast CD to test connection and it tests OK in safe mode, but says unable to communicate if in standard mode. Makes no difference if Fire Wall is off or on and if Fire Wall is on in safe mode it communicates. Suspect some service is being started in full mode that maybe causing the issue.

Can you check in MSCONFIG to see if any services or applications are running at start up that you don't need, disable them, and see if you still have an issue?

I agree with Adam. The most possible cause is the anti-virus and firewall. If the issue persists after you disable them, please boot in Clean Boot Mode, and try to find the root cause. You may check This thread for steps of Clean Boot Mode. Arthur Xie - MSFT