BelkinFD8231-4 modem problems

Belkin FD8231-4 modem trouble: After suffering wireless connection dropouts, I was called to see if I had any ideas on what could be wrong.
Resetting this modem and reinstalling all connctions, things appeared to go well, till next day, when the same problems showed themselves.
I took an asperin, googled for firmware, which I found (5 types) and applied what I saw as being the right firmware Vers 5100 with vers 5 >>
The modem now plays up with wireless (non existant) and is flaky and has difficulty retaining wired connections.
Any clues on what may be wrong. I know my friend is ready to throw this thing back as belkin....He paid a premium price and got this problem. He is not amused....