i would also keep a log every time the signal drops. i went through this with my isp some time ago and they thought i was just IE chalanged. i kept a log and showed it to one of the supervisors when they came over for a house call and they put a signal monitor on my connection.

turns out the cable in the junction box down the street was loose and was expanding and contracting with the temp causing the ocasional signal loss. in the end the log is what convinced them the problem was on their end.