I memory serves me correct, doesn't cable service share bandwidth locally, between you and your neighbors (like on a local network). With that, if the kid next door starts downloading large pron files, your bandwidth will drop accordingly. If you get two of the neighbors kids doing the same thing, then it will get worse.
Just a thought Morph ... there are those that know more about it than me, but that is a 50,000 ft view of this.