Netgear CG3000DCR and our VPN 100 firewall

Hello, we recieved the new Netgear CG3000DCR to upgrade from the old modem. We run a symantec vpn firewall that sits before our router. iit wasn't connecting, so we reset the firewall back to default settings and everything connected. It ran like this for 4 days and now it's back to the same thing. I can't seem to reset my firewall now. could there be a compatiblity issue with the modem and the firewall? seems strange that it worked fine for 4 days though. thanks for any help!

Scott