"RendererVector must be empty"

I'm still working on plotting my data on the same graph...but I'm making
progress.  After scrapping everything and using the tutorial as a
template, I'm getting a new error (hey, that's progress!)

I get this error when I add a 2nd ScalarMap to the display.  I can plot
single sets over and over again, but whenever I try to add a 2nd set to
the Y axis I get this:

visad.DisplayException: DisplayImpl.addMap: RendererVector must be empty 

Of course I'm doing something completely obviously wrong, but I don't
see it.

Also, is there an index to the examples?  I.E. "Test00.java:
Demonstrates 1, 2, 3"

Thanks!

p

------------------------
Paul Gifford, Capt, USAF
NOAA/NGDC
325 S Broadway EGC2
Boulder CO 80303

303-497-6556 voice
303-497-6513 fax