When both the PC and Cable lights go out it's usually a sign of a bad modem. Check if there is a reset button on it. If not, try unplugging it for 20 minutes or so and then plugging in back in. (Power, that is.) If the problems continue I would request a new modem since they provided it, likely at a charge to you. It's also possible that their service is on the fritz...they can reset the modem remotely, so a bad signal could conceivably do that for periods of time. Either way, I doubt it's a problem with your computer since that wouldn't result in the loss of a connection between the modem and the cable service. (That light should not go out.)
My internet just loses connection randomly in random intervals. The power on my modem is on all the lights go out except the power and i have to wait for my connection to return.
I do use a router but it does it regardless. Hmm it mainly does it during online games,but it has lost connection when just browsing etc. Oh and my old modem was a surfboard model Xxxx i forgot exact model whatever they provided in like 2001.
I just recieved a new one Touchstone telephony modem
(i just had comcast broadband phone installed) that allows your phone line to be run through modem. Which solved the problem for a short while.Im thinking it could be a virus maybe ive heard of trogan or dialers causing symptoms along these lines.