There's no way to restore all defaults at once, in 2010 you'd need to go to Tools > Global Options and in 2011 the Application button in the top Right then Options.
Once in there you would need to press Default on each page of the options.
An alternative is to Export the options as an XML from the Options page on a machine that is working correctly and Import this XML on the non working machine.
If this fails to resolve the issue, what file format are you using, how big are the spots, are these present in the native file? Can you switch off points in the View (leaving lines and solids viewable)
Lee Mullin
Construction Technical Specialist
Autodesk Ltd.