Thrak, I wonder if your problem with the 78S could be coming from a setting that you have it on. I was out caching a few days ago with the 62S and decided I wanted to change the auto zoom from auto to off. After I did the gps became very unstable and sluggish. It wouldn't update the caches and several other problems. I first turned the gps off and back on several times but at first it would work fine than back to the unstable problems. I switched the zoom setting back to auto and it started working ok again. I know your gps should work with any setting, but this was a problem I was having.