We're sorry about the trouble with Photoshop. Would you mind checking if launching Photoshop as administrator makes a difference? Did you reset the Preferences by moving the setting folder manually? If not, you can try resetting the Preferences manually using the steps mentioned here: https://helpx.adobe.com/photoshop/using/preferences.html#Manually
Yes - everything runs from an account with administrator privilages.
I reset the preferences file by holding down ctrl+alt+shift when launching Ps and acknowledging the dialog box.
When I reset the preferences using the instructions in the link provided it initially hung on "Reading Brushes" the first time it started (for about 30 seconds) (presumably whilst it created the new preferences file(s)) but then reverted to taking 30 seconds to get past "reading preferences" every time - so in essence "no change".