I've had a recurring problem with my MacBook Pro (late 2008 model, 10.8.3). I'll get a 'your hard drive is almost full' message and then, if left unchecked, a 'your hard drive is full' alert. And sure enough, when I open a Finder window I can watch as my space just trickles away to nothing. I used to have 20GB free on my drive - now it hovers at 11 or so and then just disappears.
Restart restores the space back to 11GB or so but after a few minutes it starts disappearing again. I've run the full gamut of Onyx utilities - SMART is fine, daily/weekly scripts, permissions repair. I've even reinstalled OS X from the recovery partition (it fixed a weird time machine problem that was hanging with huge backups, but not this).
This is a very frustrating bug and I need some fresh eyes on it. Any ideas what's going on and how to stop it. Feels like a runaway log or cache file but I can't work out what is triggering it. It's like playing Majora's Mask with my laptop - every half an hour I need to save everything and restart or my computer just freezes from lack of memory. Ugh. So please, help?