Have you explicitly tested this? Try to run one of the JSci examples
from the command line:
c:\> java -version
c:\> java GraphDemo

or try compiling from the command line:
c:\> \explicit\path\to\java13\javac GraphDemo.java

Given you have no problems with JSci for JDK 1.1.8 and the error message
states "...class file has wrong version...", JBuilder must be using an
old version of Java. Try searching your hard disk for all occurences of
java.exe.

>
> Um... I _am_ using JDK 1.3.1. Other than the beta version of JDK 1.4, I
> don't see what I could do...
>

--
http://fourier.dur.ac.uk:8000/~dma3mjh/

"The challenge is the motivation"