I have a black Macbook bought new in July, 2007. For the past month or so, it's been hanging a few times a week the beach ball of death comes up, and I have to reboot using the power switch. Crash reporter doesn't pop up, and when I've checked the logs, I haven't seen any common thread (no pun intended) tying the crashes together. Sounds like a RAM problem, right? That was my first guess, and I have been using aftermarket RAM for about eighteen months now. But I ran memtest for a few days (in single-user mode) and never found an error. Is this conclusive proof? If not, where should I turn next?