Well it's obviously not a new mac.

If you recently updated Quicktime to 7.0.4 then see point 3 below. If not then do the other steps.

1. It sounds like the OS update did the damage. Normally after installing Softw or updates, it's best to repair permissions. ie: Restart whilst holding down the SHIFT key until you see the window saying, Safe Booting. Then once started, go to Utilities folder, open Disk Utility & repair permissions. Then reboot normally.

2. I would suggest you re-install Java using the "Offline" java installer. Try this one: http://www.apple.com/downloads/macos...update142.html
If it refuses to install & gives you a "null" error, go to the harddisk drive, open Receipts folder, & remove/trash the last Java 1.4.2_update2.pkg package & try again to install java. See Receipts folder sample image

3. BTW if you installed QuickTime 7.04, then uninstall it & go back to an earlier version. QT 7.04 has a severe bug versus Java. See QuickTime 7.0.4 bug stops LimeWire from opening!