Unable to compile class for ...

["Wiechert, Holger" <H....@iks-gmbh.com>]

Hi, I've seen that this error has been in the discussion here a few times, but
finally has never been answered. It occures *sometimes*, when a JSP uses a java class.
To make things clear: I only use the standard tools: JBuilder4 and once in a while EditPlus
(an editor that is definitely not screwing up the files).
So the error message is:

Error: 500
Location: /myapp/someJSP.jsp
Internal Servlet Error:

org.apache.jasper.JasperException: Unable to compile class for JSPC:\test_cat2\webapps\myapp\WEB-INF\CLASSES\com\mycomp\Constants.java:1: The source file encoding may be different with this platform encoding. Please use -encoding option to adjust file encoding, or apply native2ascii utility to make source file ASCII encoding.

I use Tomcat 3.2.2, but I've seen this "error" has also shown up in Tomcat 3.1.

The file the compiler complains about comes out of a war-file. But it seems to be just as the 
original one that was packed into the war file.

Does anybody know, how to prevent this error?

Thanks in advance, Holger