I have an assembly I've been working with for a couple of days with no problems.  Suddenly, when rotating the shaded model in the display window, the geometry 'jitters' as though components are being moved, even though I am only rotating the display.  When I stop rotating, the components 'stay' in the wrong places.  If I then switch the display type to HLR, everything looks OK, but when I switch back to HLR, it is wrong again.  I have tried saving the assembly to a new file, suspecting corruption, but the problem persisted, and the file size jumped from 18MB to 226MB.  The behavior persists across SW restarts and system reboots, but other models of similar complexity don't exhibit the problem.  If I open the assembly resolved, lightweight or in large design mode, the results are the same.  It definitely seems to be something in this particular assembly. 

I've been using SW since 1998 and have never seen anything like this.  I've attached a video showing the problem.

Incidentally, Large Assembly Mode is turned off, but the display acts as if it is on.  I had turned it on briefly to see if the problem went away (it did not), and ever since the display is stuck in LAM.

Any thoughts?

Jim S.