Danny, maybe too late. I had that problem too sometimes. I think it is
like it is on overload and sort of freezes, occasionally it would catch up
with itself or I would click far far away and it would come back, sometimes
just doing another task eg make some vegetation/change the flowgraph would
help it.. When all else fails just close and start again ... saving
regularly becomes critical, I think I ended up with about 100 saves in the
end!