I’ve noticed it since MapSource 6.14.xx, 6.13.7 was the last version that didn’t have the problem for me. These have all been from maps I’ve made myself, so I may be missing some command line switches that would clear them up.
Some images and a discussion thread posted below.
http://forums.gpsfiledepot.com/index.php/topic,1115.msg7127.html#msg7127
I think it has to do with the way the newer versions of MapSource cache imagery. Control-G hit twice will flush the cache and clean up the image with newer versions. The first Control-G may blank the screen. The second will bring back a cleaned up image.
I don’t have that problem with maps I compile with cgpsmapper, but those are usually semi-transparent and non-routable, usually just topo, hydrography and woods. My mkgmap compiled maps are non-transparent and routable with a full range of data types.
I don’t notice the problem with Garmin’s City Navigator products, but the level of detail on those is much lower than a comparable area with topo.