I've had this problem for a while now, and I've been unable to figure out why. I can't even remember when it started, but it has become quite a nuisance.
The Finder window shows that I have 302GB of harddrive space remaining, out of 500GB. The Activity Monitor and Disk Utility show I have 240GB space remaining, and my System Profiler shows I have 239GB remaining. I just deleted a bunch of old TV shows off of iTunes (about 40GB worth) to open up some space, but only the Finder changed (up to 302GB from 260GB) but the Activity Monitor, Disk Utility, and System Profiler haven't changed.
Now, I'll assume the Finder is showing the correct amount of space, but I'm wondering why the other utilites are showing the incorrent amount of space. I have a feeling maybe something was screwed up when I created a 50GB Windows 7 partition through Boot Camp a couple months ago.
I've attempted to Repair Disk through the Disk Utility and it says everything looks fine. Any solutions to this minor inconvenience? Or at least an answer as to why this is happening?