try powering off the NTL modem and Belkin router.
Then power on the NTL modem, leaving it for a few minutes until the LED lights settle down.
Then power on the Belkin router and wait a few minutes for it to settle down.
That has worked for me before.
Having heard that routers could overheat and misbehave in such a way, I placed my Pre-N Belkin MIMO router (f5d8230) on a plastic box with heavy corrugations. This ensures air flow under the modem to the air holes underneath.
My occasional loss of wireless connections has never recurred since.