Hey bonehelm, I was just having this same exact problem last week. Every 5 minutes the DSL light on the modem would go off and you'd be disconnected for a few seconds and reconnected after.
I found that there was something wrong with the wall jack I had my DSL cable plugged into. Try switching to another jack somewhere in your house and try it there...it fixed my problems.
And also do you have a filter on all your phones at home?? Cuz that could be an issue also.