Discrepancy between Finder and Disk Inventory X on Yosemite

I recently got warning that my 500GB SSD was nearly full. So, I offloaded stuff in Dropbox, image files, videos, duplicates, etc. and cleared over 200GB off the drive, leaving about 170GB of iTunes, iPhoto, Documents, etc.

I then saw there was a discrepancy between Finder and Disk Inventory X. Finder shows what i would expect, 200GB free. Disk Inventory only 70GB. So, I'm left wondering what has happened to all the space I freed up, why is there a 130GB discrepancy.

Tried all the suggestions - cannot find a /.MobileBackup directory. Tried rebooting. Tried running Disk Doctor, repairing, etc. etc. Read through similar questions, but as yet not seen an answer/solution. Is there some corruption on the disk, maybe, or is this related to Yosemite upgrade a few months back (Wireless has been playing up since, and OSX has crashed a few times since then).

Finder: Macintosh HD Info

Capacity: 499.05 GB Available: 207.56 GB Used: 291.49 GB

Disk Inventory: Macintosh HD HFS+

Capacity: 464.8 GB Used: 394.2 GB Free 70.6 GB

Directories by size:

Users: 213.4 GB Applications: 30.2 GB Library: 13.1 GB System: 5.8 GB lost+found 4.8 GB private 3.6 GB usr: 0.9 GB opt: 0.1 GB

Total: 272 GB