had same problem with my NTL120 ( Notts )
called TS , answered in 10 seconds , took modem off system , back on and sent "config" file and told me to call back in an hour if still having problems
hour later still resetting , called again , answered in 20 seconds , checked levels and all were ok so arranged engineer for this morning
9.30 , nice engineer man turns up , new NTL250 modem , gone in 10 mins and all is now well
well done NTL
