Hm, is the power source the modem is running on going out?
Does your modem utilize a battery? If so is it going out?
Is the Ethernet wire running from modem to router fine? I just switched the cables a few mins ago, seeing how long it lasts.
How old is the Router? Routers a year old, modem is 4 years or more.
Is the network properly configured or did you change any network settings recently? Well its cable, DHCP auto configures it, and i set the wireless up myself.
How many computers is this network supplying for? Playstation 3, Wii, 1 desktop, 2 laptops, 2 iPod Touches.