Mike, I have a similar issue:
Apple Airport Extreme and Telus high speed (up to 15 mbps) with the Thompson Speedtouch moden.
I have to cycle (restart) the Airport router daily , sometimes twice a day, to reconnect to the internet.
I also find that when playing music, hosted on an HP EX985 MSS with my Logitech Squeezebox Touch music player, I frequently get dropouts in the music. It is connected with ethernet and the Airport Extreme is the router for this 10/100/1000 network. I never had such issues with my previous D-Link wireless N router (single band).
Honestly, I am about to take Apple out behind the barn on this. They sent me a new Airport Extreme a month or two ago, so I am actually on my second unit. Very frustrating.
I also am keen on any insight others can offer...