look's like a problem with loader.jar.
maybe extracting this archive can help?

Hi vikc.
I also got exactly the same error messages at first.
In my case, on Japanese version of CS, Windows2000 and Java 1.4.2,
I got it working by just renaming the plugin folder,
(and specified this folder as a plugin folder in Illustrator's preference).
I renamed it to "Plug-ins" from its original name of 2-byte Japanese characters.
Then I also tried with several other names of 1-byte characters and found no problem.
If you are using non-English version of Illustrator, this kind of fix might be worth trying.
Version 0.5 of Scriptographer works fine without this fix.

That's very interesting, Hiroyuki. It seems that Java cannot handle the 2-byte folder names. I will investigate this, maybe it is just a problem with converting unicode names wrongly. Vikc, do also use non-english characters in your folder name?
I strongly disencourage to use 0.5 though, as the syntax is not compatible, and the software is discontinued. It works in this case because it does not use Java internally...

Many thanks to you all.

I do use a Simplified-Chinese edition of Illustrator cs2, and the problem is solved successfully by following Hiroyuki's suggests, removing the non-ascii chars in the folder name. I believe it's caused by the Java engine handling unicode or other charset. And it's very likely that this problem will occur on other non-english users. So I would suggest list this info in the install instrution.

I get Sg working now, thanks for your help again.