its a hard one to diagnose because a power fluctuation could also be causing this, although if a reboot of the modem always fixes it, then chances are its not that.
sadly it took me ages to sort out my problem with NTL which did turn out to be a problem with the upstream.
I made sure NTL were aware of the problem from day one and I asked for a full 3 month refund which they gave when it was all fixed.
ring tech support and they will send someone over, probably wont fix it, but will at least get them to check that off their list... then you can badger them to provide a different modem....
good luck, we need the sm47 caps up without any hitches
