The DHCP (Dynamic Host Configuration Protocol) Server is what allocates the IP addresses to the computers that connect to the router.
It appears that some form of interference is breaking the wireless link and causing the "clients" to lose their IP address. Toggling the router's DHCP server off/on will cause the IP addresses in the client PCs to be renewed.
Try giving one of the clients a fixed IP address in the same subnet that is currently used. For example, if the router's IP address is 192.168.1.1 then give the client an address such as:
IP address - 192.168.1.50
Subnet Mask - 255.255.255.0
Default Gateway - 192.168.1.1 (the router's IP address)
DNS Server address - 192.168.1.1 (the router's IP address)