Linksys Cable / DSL :: WAG 320N Why Can't Both Modems Operate Wired And Wireless

I have my broadband line feeding into a WAG 320N in an outside room.   There are computers in the outside room which are wired to the modem via CAT leads & plugs.   Wireless is turned on, but is not currently being used in this room, as the wired connections work fine.   From this outside room there is an underground cable (12 metres) to the house, which through a CAT lead is plugged into another WAG 320N,  which operates primarily wirelessly,  so laptop computers can be used in the house wirelessly.  When the outside room modem is turned on AND the house modem is turned on, only one modem OR the other can access the internet, NOT BOTH.   Why can't both modems operate wired and wirelessly.   What is the problem?   Is there a conflict between the two wireless signals?   Can/ should I turn off the wireless signal from the outside modem (if so HOW?) . OR is there a way I can have both modems transmitting a wireless signal.