Airport Express and Verizon FIOS Actiontec M1424WR

Hello all,

I have been trying for the life of me to try and get Airport Express to extend the network frm my FIOS router, but I have been having absolutely no success. I go through the steps suggested to extend it and get nothing.

I have tried a few different ways, including one way of trying to set up a WDS using the router but that failed because I suppose the router doesn't exactly work with it, or something. And I should actually point out that yes, it is a cable modem. Pardon my use of the word router.

Anyway, I open up airport utility and do the following (version 7.3.1):
I set wireless mode: Extend a wireless network
Choose network name: (my network)
Set wireless security to WEP (what my network uses): *insert code here* twice...
And have it set to accept wireless clients

The internet setting is set to use DHCP since that is what the cable modem is set up to do. Actually I can't change the settings of the cable modem unless they are something small, because it is a shared connection.

So, I do all of these things and I never get it to work. It continues to flash yellow and doesn't want to connect to the modem to extend the network. I don't know what to do.

Any help would be appreciated.