IDLgrContour is hiding

[Pavel Romashkin <promashkin(at)cmdl.noaa.gov>]

Hi,
I am having a problem with IDLgrContour. Is it a strange object, or is
it just me? I can't seem to make it show anything at all:

w = obj_new('IDLgrWindow')
v = obj_new('IDLgrView')
m = obj_new('IDLgrModel')
p = obj_new('IDLgrPlot', findgen(10))
c = obj_new('IDLgrContour', findgen(20, 20))
m -> add, p
m -> add, c
v -> add, m
w -> draw, v

and I see no indication of the Contour object in the window, although
Plot appears just fine. Aren't they both graphic atoms, so you use them
more or less in the same way? What's even more interesting, repeated
re-draw causes a floating-point error and actually removes even the plot
from the window. Leave alone that I tried it in a program first and it
caused a heavy crash of the entire OS :-(
Am I missing something?
TIA,
Pavel