Probably something stupid I am doing, but the range display for all elements has disappeared from my animation timeline.  I can add and remove elements, I can drill down to their sub tracks, but the actual track displays to the right are just horizontal lines.  There is also no slider at the bottom to move along the range, as if it were zoomed in.  the animations still work etc, and I can see the timeline control bar, but nothing in the main "graph" area where I would normally see my individual tracks and time markers etc.