Wireless computers in my house can connect to the Linksys WRT150N, but not the internet.

The Linksys is attached to a modem and I have tried an alternative cable that I know works (I'm using it here now as well as that modem, so they're fine)).

I have done a Factory reset. I have loaded a previously saved configuration file. I've pressed the reset button on the back, which worked as the password went back to the default.

I've tried 2 computers with the same result, both of which had no changes to them since last successful connection.

Is there anything else I should try before replacing the unit so I can again connect to the internet?

Thanks.