My experience with Belkin kit has been consistently poor, although I know some people can make 'em work. I splashed out on a Draytek Wireless Modem Router, and it's been stunningly good. I have an older Netgear up at the cottage, and that's been fine, too.
Do I understand that everything worked OK, then the old one didn't. The new one doesn't either? If so, maybe a neighbour has got a new high-power device (not necessarily a WiFi router) transmitting on 2.4GHz.
As SD says: try experimenting with different channel numbers. Move as far away from the one it's on now as possible - that may get away from whatever's clobbering the signal.