Looks like there is a new version of ArcGIS Explorer available (Build 350).

New Features:

• Keyboard navigation while using track line or track polygon in the measure and create notes tasks
• Vertical altitude (elevator) navigation has been added.
• New Unit options for the Position Status bar: MGRS and U.S. National Grid
• Improved functionality for Go To Location: support for MGRS, USNG and decimal degrees. In addition, the ability to Create Results of the location
• Clouds, stars, atmospheric halo are map properties of each map and are stored in the .NMF rather than properties of the application
• Set Home Server restarts ArcGIS Explorer automatically

Fixes:

• Once the globe is pivoted and flying has started, the zoom in key functions correctly
• When the most recent click is on the application’s title bar or is not on the map, focus remains on the map
• Scale thresholds are honored for local shapefiles
• Add Content for KML can be added via URL
• Once added to the map, KML files are listed in the correct order in the Contents
• ArcGIS Explorer can open a .NMF file containing a globe service with group layers
• The application disables the “->” button when the “custom tasks” heading is selected
• LayerResult appears in the correct layer order
• Polyline and polygon length properties have been corrected

Fixes to the ArcGIS Explorer SDK for .NET (Build 350):

• Calling GetSymbolNames(esriE2SymbolType.Unknown) no longer gives the error ‘Value does not fall within the expected range’