In their infinite pushy wisdom, Apple has broken Java in their update of Mac OS X to 10.3.9. If your favorite Java applications are no longer running (try java -version at the command line... you'll likely get a segmentation fault), the current fix (from MacOSXHints.com) seems to be:
Download the older update to Java: Java142Update2.dmg
Remove
Java142Update2.pkgfrom `/Library/Receipts/'.Reinstall the Java 1.4.2 update. Reboot.
Run Software Update and reinstall Security Update 2005-002. Reboot.
Unfortunately, this means that you'll be running an older Java framework than the bleeding edge as released from Apple... however, until they can get their shit together and release something that doesn't seg. fault, we'll have to use an older framework to get things done.
UPDATE [2005-04-18 10:47:03]: Well, none of this worked for the one Java app that I've been using a lot lately. In fact, following the above instructions wouldn't even allow me to install the older version of Java. I was able to download the security update and install that and this seems to have fixed incidental Java crashes (of the java -version type). Ho hum.