Try
a SAFE Boot & Repair Permissions
I was going to suggest reinstalling Java but I don't think OS 10.1 is compatible with Java 1.4.2 & installing the
Mac OS X Combo Update 10.1.5 might seem a bit of a pain. Could try
Jum's Build to see if it makes any difference. This is a beta of a beta but generally works fine. I never had any problem with it.