Matt,
Beginning with, I believe it was 7.3, the latitude and longitude
entries in the table can be numeric values
or parameter names (TPP or Derived) and the overlay should update as
parameter values change.
Without seeing how your parameters are set up, my suggestion would be
to validate your equations and
ensure the latitude and longitude values are within valid ranges. You
can also email us a copy of your
config if you'd like us to take a closer look.
Mike