[idvusers] Error generating graphic from command line

We have just recently installed IDV 3.1u1 for Linux and have been able to
get everything to work except for generating PNG graphics when running IDV
from the command line.  I am trying to open a simple bundle and generate a
basic output graphic using an ISL file:

runIDV -islfile scripts/MUtest2.isl

We have been able to successfully run a very similar .isl file that creates
a PNG file when ISL is launched with the GUIs.  (run IDV, create a simple
plot on the default loaded map, then Open menu > ISL file)

We are stumped as to why we can create a PNG running the software through
the GUI, but get this OFF_SCREEN error when run through the command line
with the -islfile argument.

here is the error:

[root@ddc-ls-eddy IDV_3.1u1]# ./runIDV -islfile scripts/MUtest2.isl
Java 3D WARNING : reported GLX version = 1.2
    GLX version 1.3 or higher is required
    The reported version number may be incorrect.  There is a known
    ATI driver bug in glXQueryVersion that incorrectly reports the GLX
    version as 1.2 when it really is 1.3, so Java 3D will attempt to
    run anyway.
JAVA 3D: OpenGL 1.2 detected; will run with reduced functionality
Java 3D ERROR : FBConfig doesn't support pbuffer or pixmap returns None

OFF_SCREEN_BUFFER_ERROR: Renderer: Error creating Canvas3D off-screen buffer
graphicsDevice = X11GraphicsDevice[screen=0]
canvas = visad.java3d.VisADCanvasJ3D[canvas0,0,0,878x825,invalid]
[root@ddc-ls-eddy IDV_3.1u1]#

Thanks for the help,
Mike U