Hi Eve,
You seem to be doing everything correctly - though using a very old version of the Radiance Control Panel (there is a free upgrade available for both this and Ecotect v5.60 which you are entitled to).
In your images, it is clear that the Radiance command pcompos is receiving a bad image at one point and then crashing big time at another. Radiance does this kind of processing as a chain of commands, so any failure at any point causes problems.
Unfortunately pcompos is part of Radiance so I'm tempted to suggest that you try to download the very latest Desktop Radiance 2.0 Beta as this problem isn't common (http://radsite.lbl.gov/deskrad/download.htm).
In fact, I would consider downloading the MingW HEAD version of Radiance for Windows from:
(http://www.bozzograo.net/radiance/modules.php?op=modload&name=Downloads&file=index&req=getit&lid=22)
However, it could also be because the location of the scene/image file is in a folder with a space somewhere in it's pathname. For good measure, try running it again by exporting your model to a Radiance file in a directory with absolutely no spaces, something like "C:\Temp\Rad" and saving the scene file to "test.rad". Saving it on your Desktop or to your Documents directory is actually to "C:\Documents and Settings\[UserName]\..." so there are two spaces around the 'and' bit...
Spaces cause problems because the early versions of Radiance for DOS didn't wrap pathnames in quotes, so any spaces in a filename or path would mean invalid command lines sent between the individual tools. The later versions of DesktopRadiance and also MingW seem to handle this much better.
Hope that helps...
Andrew
--
Dr. Andrew Marsh
Ecotect Support Team
Autodesk, Inc.