Linksys WRT54G won't link to Motorola Surfboard

I just bought this Linksys WRT54G, and it won't connect to the Motorola Surfboard modem. I can connect to the router wirelessly from my Macbook, I just can't get online. I'm sure it's the router's problem because I can't even log in to the modem when I'm connected to the router. I checked all my connections repeatedly, tried firmware updates, and many many power cycles. Also did a lot of googling and tried other solutions. Are they just not compatible with each other?

One thing is though, the very first time I hooked it up, it was working. Then I power cycled it and it won't work now.

When all else fails with power cycling - make sure you power cycle all the devices. Unplug them all and begin with turning the modem back on. Wait until it is showing data connection, then the router and wait 30 seconds, then the computer.

Also do you have the settings correct for your Cable service? On the WRT54G it's usually the first page of the setup. You connecting to 192.168.1.1 on the linksys with a browser? Check the settings. I don't know who your cable provider is but there is DHCP that works with most cable modems and providers I have set up for people.

Also try what Bobtomay suggested.

OPPS: forgot one important and often overlooked thing. I know for sure Comcast for one uses MAC address's to control how many computers you can connect to the net. If the Surfboard was hooked directly to a computer when your cable was set up, and your cable provider is using the MAC address, you need to clone the Mac Address of the computer into the router. If you look on the first page of the router setup, there should be a tab that says Clone MAC address. I am not sure if your Cable provider is doing this or not, but here with Comcast you have to clone the IP of the setup computer into the router or you will not get an IP from Comcast.

Thank you very much bobtomay. I guess I didn't try powering off all the devices at the same time, and power them up one at a time in order. Thanks!