I was just playing around in the Java folder and noticed the default applet is set to 1.4.2. However there is a version 5. so why isn't Tiger using the latest version?
There was a J2SE 5.0 Release 4 update back in April that should have switched your default to 1.5, you may want to reapply if /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK isn't pointing there.