Problems connecting SMCD3G-CCR modem to ASA5520 firewall

Our company recently purchased Comcast broadband to replace our T1 service. Before getting rid of the T1 though, it's my job to get the Comcast connection up on the ASA5520's interface. The problem is we cannot access a test website after setting up the interface on the firewall. We were assigned a block of 5 IP's and the router was configured for pass through service.

The troubleshooting I've done:

Connected a server and assigned it a static address from our block to verify we could get internet. Check! We have internet, Yay! I connected another service provider to the interface on the firewall we wanted to use for Comcast, assigned the correct IP setting for the static route, interface, NAT and Access rules....and we could see the test website.Yay! Changed everything back to Comcast and ...nothing.

I ended up calling tech support, who verified that they could see the interface IP on the firewall and on the server I had configured, so that's a good thing. They couldn't explain why traffic wasn't going through though and recommended bridging though he admitted he knew nothing about that stuff, so that wasn't any help. I did ask him if having DHCP and DNS running on the router would conflict with our AD server, but he said he didn't know. Well, me being the curious type decided to shut it off on the router...to no effect, same thing..nada.

So herein lies the problem. Is there some setting or something that needs to change on the Comcast router? Thanks!