SOLUTION:
I have diagnosed the problem; It relates to using dual screen with two separate graphics cards. The problem can be tested for by running AE full screen on one monitor and then the other. The issue should present itself on only one of the two screens. Once addressed I have been able to run AE on either screen OR spanning both without issue.
TO SOLVE:
With After Effects CLOSED, open Nivida Control Panel and select 'Manage 3D Settings'. Choose 'Open GL Rendering GPU' in the list of options and select either '1 of 2' or '2 of 2' but not 'Auto'. Apply changes and the re-open After Effects.
I very much hope this saves somebody some time!
Ben
