Just fixed the problem by doing the 'software update' function via the internet connection; the latest firmware was dated from early in 2011 (dont recall exact date) ..I was still at firmware level from 4Q2010. It also just so happens that Netflix sw app underwent MAJOR upgrade -- screens and functionality VERY different. I'm guessing this is what caused the problem. It certainly would have been nice if Samsung or Netflix had informed us that the major Netflix upgrade required upgrade of the firmware!
Been using Netflix on LN55C650 for a year; today suddenly Netflix can't access internet; internet connection works for all other internet@TV apps so connection is fine. The internet@TV Properties screen has the follwing info: shows 'NetFlix ESN: SSLT-LC6P-100202-0000245542-0E7E (deactivated).' When I attempt to connect to Netflix, asks if I'm a member, respond yes, the the activate code screen appears for half a second but then gets overlaid with screen saying 'Netflix cannot access internet. Make sure your device has active internet connection.' So it's just Netflix that can't access internet.