SolidWorks (SEK) 2015-16 won't rotate model (w/ mouse) past 180deg in X

SolidWorks (SEK) 2015-16 won't rotate model (w/ mouse) past 180deg in X & Z axes. Y axis works fine. I have had the software for just over a year and a half, and never experienced this issue.  It worked fine last Thurs morning and didn't Thursday nite.   When I reach the 180 deg "limit" using the MMB click and drag, the model stops rotating, no matter how far move the mouse. I move the mouse in the opposite direction the model, or assembly, will rotate for exactly 180 degrees, the stops rotating. If I use the arrow keys it works as designed.  If I take my models and assemblies to a school computer it works fine.  If I create a model or assembly on a school computer and bring home to mine, the problem presents itself.I have tried the following with no success: 3 different mice; click Options, Reset, Reset All Options; Uninstalled SolidWorks and re-downloaded a fresh program; Restores computer to 3 days before the problem exhibited itself; talked to my instructor who has been on the Beta Testing Team since very near the beginning.  Since there is no official Tech Support for the educational version I hoping to find some help here.  No suggestion is too small. Thanks in advance!
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