Most if not all Cable modems are just that, A Modem, where as most current DSL modems are also Routers with Wireless Access Point (WAP).
So the question is when you went Cable did you also install a Router that has Wireless in it and have you set that wireless up correctly.
Post make & model of both Modem and the router you are using.
And yes it is NOT the cable companies fault.
Thanks. We have been using an existing Time Machine for wifi. Cable modem replaced DSL router and was hooked up to Time Machine. What's odd is that 3 computers and iPad2 are connecting to home wifi just fine, using exact same network and password as before. My Mac book pro and an older iPad are not. IPhones are also connecting to home wifi just fine. I managed to get my Mac book pro hooked one time by copying ip address from a Mac that was working (entered manually) then turning that one off. That's not what I need.
The error message is "no ip address".