Pick one device to be the wireless router. If you want it to be the Linksys, then you should read up on how to put the Actiontec into bridged mode. Typically ISPs don't support that configuration. And if you just want to use the Linksys as a wired switch, then simply shut off the wireless in the router configuration.
I have Verizon FIOS broadband for my Internet that uses an Actiontec MI424-WR wifi router (provided by Verizon). I also use a LinkSys BEFSR41 wired router as a switch to extend the wired ports beyond the 4 ports that the Actiontec provides. When I had it connected, two laptops that we have in our house running Windows 7 would not connect wirelessly. A Verizon tech came out to troubleshoot the issue and found that if the LinkSys BEFSR41 was disconnected from the Verizon router, the Windows 7 laptops could connect. He reconnected the LinkSys and the problem returned. The problem is I still want to use the LinkSys but do not know how to configure it so it does not interfere with the Verizon wireless. Someone at my work said I may have to try to set the LinkSys up with a different Gateway and/or set it to use a higher set of IPs like xxx.xxx.xxx.100 - 200 so it does not interfere with the lower IP range. How can I configure this?