Not really sure I use adsl, I would ask for your attenuation figures but your uisng cable not adsl, check all leads and virus's spyware etc, call the company and get someone out to look at it.
Needed Operating System:
Internet Service Provider:
Within/Outside Local Network:
Other Software Using Network (i.e. AIM, Bittorrent):
These are things that are needed for troubleshooting network issues.
I personally have to unplug and replug the power to my linksys router and cable modem (roadrunner) I do it about once a day, its annoying but I just live with it; its better than dialup thats for sure.