It's just an indicator that you are in the hyperMILL section and if you select any Inventor function (sketch, line, circle, extrude....) it switches you to the Inventer section. It's the same logic that Inventor uses, example create a sketch and draw a circle. RMB and your option to finish the command is - Done or ESC key. So to finish hyperMILL functions hit the ESC key as well.
SpaceBall has no problems in the older versions on Inventor but I did notice the same problem with SolidWorks 2008. Maybe we need to contact 3Dconnexions about this issue with the newer graphics in the latest software.
Hope this helped.