'Disk full' message even though 14gb is shown as available by Finder
I've started to receive a 'Disk full' message when every indication shows that I still have over 10GB of hard drive space available. The bar at the bottom of the Finder window, the 'Get Info' screen, and Disk Inventory X all show that my space usage is about 10GB under the size of my available disk space.
The problem is not limited to an error message - web browsers will also sometimes refuse to download now because of 'disk full' issues. But if I try to copy files within Finder, it always works, up to the actual limit of the disk size. This suggests that something is going on with file management where both MacOS and my web browsers see that there is no space, but Finder is able to manage around it when I try to copy files. Is this a known issue? Are there large temporary files which are not reflected in the available disk space indicators?
I'm using an early 2011 MBP with 10.6.8, and the original 500gb hard drive. I did just upgrade to 8GB of RAM but it's not clear if this is related or a coincidence.
MacBook Pro, Mac OS X (10.6.8)