Bob: Thanks for the reply. I wish I could upload an image of the map showing the problem. I know that the underlying line I mentioned is not a map feature and I doubt that it is a track log filtered down to the 500 pt capacity as there are simply not enough pts for that. Also, It is not something that can be detailed with a right click. My description was pretty poor as I had intended for the "jagged line" to be a description of the "underlying line". To hopefully clarify, the line is actually maroon in color, with a thin white line running up the center.
In addition to running under the track, it also appears as a straight line from my home, where I calibrate the unit (followed by turning it off) and the location where I turn the GPS back on to begin my track. This has occured when traveling a few miles from home and another time when flying from California to Colorado, leaving a straight maroon line from my home halfway across the country. Once the unit is turned back on at my destination, I get both the standard track, and the maroon line as described. The maroon line does not appear on the GPS screen, although the track does. It only appears on the computer screen in Mapsource.
My gut tells me it has something to do with the navigation function on the GPS, but I cannot find a setting that would account for this. I appreciate any ideas you might have. Steve