Re: [Cable HSI] CMTS channel moving and DOCSIS 1.1 and 2 modems
3mbps is fine for netflix, as long as your connection is solid. You wouldn't want to be streaming any other video sources at the same time or do anything else bandwidth intensive, but it will work just time. You won't get "HD" video however.
My guess, you have borderline signal or the modem is failing.