DHCP On Router No Longer Able To Give Out IPs

Why is it that the dhcp on my router is no longer able to give out ips or rather it assign them as for as it concerned as it will list say 199.170.0.102 but the device will have none or make up one for it's self and never get the ip that the routers dhcp gave it this happens on all devices. I know power cycling will fix it temporally but usually it will start doing it again in a few hours also I know that I can use a static ip this was my way around this problem but I have one device that won't use nothing but dhcp a printer. I had an old linksys router that did this and I figured it's old it's slow time for a new one after a few months it started, some computers are on the fringe of being able to get a signal but are still fair also even with static ips they sometime stop connecting and we have to disable the connection then reconnect to fix it the router is a dlink 615 dual band set to only G/B because 1 most devices only g 2 the one computer that has a wireless n is 70 ft away and works better with g.