new airport extreme, bridge mode, NAT

[cleung]

I just bought a new Airport Extreme as my old one which was probably 7 years old required restarting every day. My setup is as follows: DSL cable modem to Linksys Router (for a long set of convoluted reasons, I can't remove this layer) and then Airport Extreme. This is how I had it set up with my old one. The only difference is I recently started looking into using "Back to the Mac" on MobileMe and in order for it to work, I set my new Airport Extreme to Bridge mode due to dual NAT. I have an iMac, PC, MBP, MBA, iphone 4, AppleTV and ipad. All was working fine last night when I set it up. 24 hours later, for some odd reasons, I can't have my PC accessing the wireless network at the same time. If I did, it would knock my iMac off the network and says some other device is using the same IP address. For a while, only my iMac (my main computer) can access it and even my iphone can't. At this very moment, my iphone, imac and MBP all have access to the wireless network. My MBA and iPad has no internet connection. Help!