Sorry I have several question relative to the same problem.
I am using Netbeans 6.8 on OSX 10.5.8 with java 1.6.0_17 and after about 5 minutes of work, the cpu usage
While this is hardly an easy solution to implement quickly, I find that running Netbeans 6.9 on a multi-core processor works. While it might ramp up on one core, the other (3 in my case) are still free for other tasks. Given that you're on a Mac, YMMV.
Of course, it would be better to avoid the CPU hog in the first place, but if you can't find the source, but still love the IDE (as I do)...