Every single night during prime time I've been having horrible internet as well. Latency is all over the place in games, getting disconnected, etc. The SNR and Atten are fine and normal. It's apparently packet loss. When I run a program to continually ping google I run a steady 10% loss and also see 10%+ packet loss while on a teamspeak server. It's bad enough I only have access to 4mbit/768kbit but then not even being able to do what I'd like during the evening is too much. I'll be contacting Frontier and complaining.
I'm in Pennsylvania, so I'm fed from Rochester.