safe boot, permissions repair, reinstall java, and retry in a new admin account (to make sure it's not some corrupt setting in your current home folder).

These have all been suggested before, so something was missed along the way I guess.

Other than that, an other factor would be the entourage/explorer, vs Safari/Mail, but I doubt that would make such a difference. Virus protection software? Really, these are just guesses since your setup and machine look to be more than enough to do much better. LW 4.2 is fine itself, and you've already done a clean install, so I doubt the installer was the problem.