One of my end users (only one) has an odd issue with his machine.  If he is working on multiple models and attempts to minimize one, randomly Solidworks will freeze. It will stay this way for a few minutes or until he selects another application and goes back.  Then it is minimized and working correctly.

I have removed the drivers for his graphics card, reinstalled.  Replaced the card with another known working sample.  Removed and reinstalled Solidworks completely.  Nothing has resolved this issue.  The only one off is this is our only Lenovo based workstation but matches the specs of the remaining part for part.  No other machines have this odd behavior.  

Thoughts?