I often find when using the desktop version that the map zooming shortcut keys (up arrow and down arrow) stop working.  I haven't been able to figure out a pattern of events that leads to this.  When this happens I can still zoom the map by going to Program | View | Zoom | In, but that's tedious.  I've never experienced this problem on my phone; only with the desktop version.  Is there a way to avoid this, or a way to restore the shortcut functionality when this happens (short of shutting down and restarting the program)?