VoiceAttack uses the standard Windows API to move the mouse cursor, so if an application is stopping the cursor from moving it's likely affecting the underlying system, rather than VoiceAttack itself.
According to the NaturalPoint website, the SmartNav software has not been updated since 2012, so the difference between Windows 7 and Windows 10 behavior may be caused by a change to the Windows input system.
Have you tried using a mouse move action using relative movement to move the cursor off that bar?
E.G. using the "Adjust the Mouse Cursor Location" section of that action, setting the "Move up" or "Move down" option (assuming you have that bar set up horizontally, making its height the smallest dimension) to, say, 50 pixels; Try that with the "Move using relative data (useful for 3D games)" option checked, as well.