More computer trouble

Yesterday the same computer that had the drive die on it last week developed a memory problem. Started rebooting and kicking programs at random. Ran memtest86, yup, dead. Jenn picked up a cheap 256M generic DIMM for me when out shopping (thanks!) to keep me going while I get this one replaced (Corsair, lifetime warranty).
One of the other drive is making an extra thump (one more than usual) on the occasional startup, but they all work OK and I get no SMART errors, so I'm crossing my fingers.
Hope this isn't something crazy like a bad power supply causing these failures.