iMac 10.6.8 started dropping wifi connection through gateway

Hi everyone,

I am looking for an advice on what can be done with iMac(10.6.8) that suddenly started dropping wifi connection. My roommate is an owner of Comcast service and has a PC that is working as a gateway for our wireless Internet connection. Both of us had the problem mentioned and after checking with Comcast bought a new router, Cisco Linksys E1200. Now her internet works fine. My iMac, iPad and Samsung III galaxy, however still dropping connection every couple of minutes. IP addresses of all three devices are in the range of IPs that are allowed to be connected to the network as configured on my roomates machine. I tried adding new locations, turning wifi on and of, rebooting maching, restarting oth modem and router - nothing doing. She had the same problems recently and one of the things that she done was changing channel. Should I try the same? Any other advices will be highly appreciated.

- Irina