Another issue might have to do with DNS. You might want to change your DNS server settings from the defaults provided by your ISP to something else such as Google Public DNS or OpenDNS. I had issues with my phone getting disconnected from my network when I had a WP7 and used my ISP's DNS servers. Changing DNS servers eliminated the problem.
The router's IP address will probably be 192.168.1.1 or 192.168.0.1 (although some routers have different IP addresses). Enter the IP address for your router in the browser address bar, enter the administrator name/password for the router, and change DNS servers provided by your ISP.
I'm using OpenDNS on my network.