Since you're still using Java 1.4.2, might I suggest you re-install Java using the standalone installer: http://www.apple.com/support/downloa...update142.html
This is more often than not, a java issue where your java hasn't installed properly or similar issue.

BTW if it comes up with an error when trying to install the Java: You get the "null" message in the Apple installer when a OS X thinks a more recent version is installed. Double-click the harddrive icon, open the Library, open the Receipts folder, then find the file: Java1.4.2Update2.pkg, delete it and try again.