This is the trick that helped me install Java 1.4.2 with no errors from software update. I searched for and wide for this information so I thought I'd share it; it's adapted from a versiontracker comment.
Apple's Solution to 1.4.2 update over 1.4.1 problem ... AppleCare's advice is to find the directory QuickTimeJavaUpdate.pkg in /Library/Receipts/ and delete it. Java 1.4.2 will now update. It worked for me on two computers that suffered from this bug.

