You should no be prevented from accessing your router configuration using your browser and the router's IP address with OneCare installed. If, however, your router configuration is being done from a program, you may need to allow it in the firewall. To confirm this, open OneCare, click on change settings and temporarily disable the firewall and see if you can access the router.
What is the make and model of your router? Can you access the configuration from either PC?
-steve