Impact Tutorial Error Message

I was going through the HTML tutorial, and I got to the section where I was required to save the Test-Rect.in file, and switch to the Processor section. I get an error when trying to save the file.

"Error: java.lang.ClassCastException" or
"
"Error: java.lang.ClassCastException j3d._Element4"

I would like to complete the tutorial, does anybody know how to resolve ?

Thanks
Robin