First, disconnect the modem from the router. Log into the router and change its address to 192.168.1.2.
You should also make sure that only one of the modem or router has its DHCP server enabled (i.e. is issuing IP addresses to the network). Set the range to start at 192.168.1.3
Reconnect the modem and router and try again. Make sure that you connect the modem to the router's WAN port (sometimes called the uplink port).
If you still cannot connect, it is possible that you meed a different type of ethernet cable to connect the 2, a cross-over cable.