You are asking about the IP Time to Live. It is an an 8-bit header field in every IP packet, set by the orginator, in this case YOU. What happens normally is every time your packet is routed it gets decremented by one, somtimes it can be by more than one but I won't even talk about that. Once this value hits 0 the packet will be discarded and will never reach its destination.

With the information you have given, it is unlikely that you are describing a TTL problem. If this were the case, chances are you would have problems connecting to start with, however with the internet being the way it is some of your packets may take different routes to the same hosts and you could run into a ttl problem this way.

To the person who said you need to do pings every couple of minutes to stay alive, this may be true on analog dialup. With cable, however you don't, it is always there, always up.