You must mean 1.3ghz right? I got the same used too. Panicked right out of the package, and I took
a bad RAM module out and it worked great. Now it's doing the same thing, after I installed Tiger.
So I went back to Panther, and it's kinda still doing it. I don't know what to do, I could take it to the Geniuses at the Mac store, and if it turns out to be RAM, then I guess I'll tell them thanks and go get my ram at OWC, LOL!
Hell, this deserves its own post.