Okay, guys. I've got a strange one for you. My iMac is having its hard drive space eaten up by something and I have no idea what it is. I have about 80 GB free on the drive. Once I login to the computer, the amount of free space slowly starts decreasing. If I leave it alone for long enough (generally one full day), it will hit Zero KB and things will start breaking. All I have to do is restart the computer, and suddenly I have 80 GB free again and the cycle starts all over. Now, I have waited for it to hit Zero KB and then run both OmniDiskSweeper and WhatSize to try and determine where all my space has gone. This is the truly weird part: I can find nothing. I've looked at the drive when I've had 80 GB free and I've looked at the drive when it's been at Zero KB, and I can't see a difference. I certainly can't find anything out of the ordinary that's suddenly eating up 80 GB of my space. I'm at my wits' end here. This has been going on for a little over a week now and I've been sure I could resolve it several times, but up to now I must admit defeat. I don't have any programs running aside from my normal startup items (background apps), and as far as I can tell, nothing has been added to my list of startup items (either in System Preferences or under /Library or ~/Library) since this problem started. Is there anything anyone could suggest to allow me to monitor what is writing to the disk, or see where the space is going, or anything else that might help? This is a very weird situation and I've never seen anything like it before in all my years of Mac ownership. (And I'm an IT guy, too!) Any assistance would be most appreciated.