That must be a huge file since it occupies all the 15+ GB you leave free on your computer at all times.
Try starting your computer with the shift key held down and work in Safe Mode.
Mac OS X: Starting up in Safe Mode - http://support.apple.com/kb/HT1455
What is Safe Boot, Safe Mode? (Mac OS X) - http://support.apple.com/kb/HT1564
Safe Boot takes longer than normal startup - http://support.apple.com/kb/TS1884
Great advice so far!
First, Safe Boot , (holding Shift key down at bootup), use Disk Utility from there to Repair Permissions, test if things work OK in Safe Mode.
Then move these files to the Desktop...
Reboot & test.
PS. Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive.