I think he may be using GPSUtility which is a nice data editing tool which has been around (with updates) for many years. It will open and display GPS Waypoints, Routes & Tracks on any georeferenced maps files. Recent improvements to MapSource (mostly with tracks & maps) have reduced the need for GPSU
I don't have an answer for the problem other than to suggest checking for current version of GPS firmware and of GPSU. Falcon, have you had any luck transferring any data using GPSU on your current computer and the 276?