Linksys Wireless Router :: Breeze To Set-up In Place Of WRT54

I have Network Magic Essentials and use a Linksys WRT54GS router.  I just received a Cisco Linksys 2500  and assumed that it would be a breeze to set-up in place of the WRT54, so that I could gain faster internet and improved range.  After about six hours of frustration trying to set it up, I am pulling my hair out!  I live in a remote area near a lake, and our only option here is a

Wi-Fi signal beamed to our homes via an antenna, coax cable to a "radio" ( Alvarion BreezeAccess).  This has always worked very well with the WRT54, but with with the Cisco 2500, I can get on my local network just fine, but I cannot get connected to the internet.  I can disconnect the 2500, and reconnect the WRT54, and get right back on the internet.