Wireless problem

I need help ..
I've been having this problem for quite awhile now , and it realy iritates me ..
I can have good wireless connection with my laptop and PSp , but after every 1 1/2 - 2 hours , it says " local connection". I dont think so it's a problem with my laptop becoz I have been using several laptops to check but there's no problen .. When I try to use two laptops and my PSP, after awhile the connection will appear as "local connection only" on the laptops and PSP all at the same time.. It takes 20mins or so for the connection to be OK again ..

I still dont know with the modem, but I had been trying to connect from the modem wired to the laptop , and there seems to be no problem, I can go online for hours without interruption... unlike when I have the router ..

I need help and suggestions .. thanks ..