The other section on my Mac's disc space is taking up all of my space!

Question

Hello!
I'm having some major problems with my Mac's other memory (as you can see).
A few weeks ago, that yellow bar used to be pink (indicating Backups). At that point, I got the "Your startup disk is almost full." message, and after making sure all my files were backed up, I executed the sudo tmutil disablelocal command. After a few minutes, I checked back on my disk space, and it looked exactly as it does now (except that I've turned the local backups back on here to try and fix it). So what I think happened is that the delete was interrupted by something and the backups files are still there, but corrupt, so they are no longer viewed by the system as backup files.
Yesterday, I took it to the apple store and the genius I talked to told me to just remove some of my big files. For instance, I had a 20 GB Windows VM on the hard drive. So I followed his advice and bought a 1TB drive, on which I put the VM, along with some big programs and files. After those big files were gone, the yellow "other" bar made some progress (backwards, of course). But even moving the absolute biggest file on the machine (according to DiskInventoryX and OmniDiskSweeper) didn't change the majority of the bar. So that makes me think that there are some files that I don't have permission to see or use that are taking up my space. Here is a screenshot of my OmniDiskSweeper scan (that's it, I checked):
If you do the math (or just look at the title bar of the window) it says that I have 77.2 GB of space used up. Unfortunately, you have to realize that it actually didn't scan everything. The software's being honest: if it can't see a file, it takes up no space (0 bytes). For instance, take my users folder:
My users folder takes up 27 GB. But the admin, guest, and service accounts combined take up 0 bytes. No way. So one of those 0 byte folders must be the culprit. The question is, which one? Any help would be appreciated. Thanks!
Mac information:
MacBook Air, 13 Inch, Mid 2012
Intel HD Graphics 4000
2 GHz Intel Core i7 Processor
8GB 1600 MHz DDR3 Memory
OS X - 10.9.4 (Build 13E28)

Answer 1

ODS can't see the whole filesystem when you run it just by double-clicking; it only sees files that you have permission to read. To see everything, you have to run it as root.
Back up all data now.
If you have more than one user account, make sure you're logged in as an administrator. The administrator account is the one that was created automatically when you first set up the computer.
Install the app you downloaded in the Applications folder as usual. Quit it if it's running.
Triple-click anywhere in the line of text below on this page to select it, then copy the selected text to the Clipboard by pressing the key combination command-C:
sudo /Applications/OmniDiskSweeper.app/Contents/MacOS/OmniDiskSweeper
Launch the built-in Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window by pressing command-V. You'll be prompted for your login password, which won't be displayed when you type it. Type carefully and then press return. You may get a one-time warning to be careful. If you see a message that your username "is not in the sudoers file," then you're not logged in as an administrator. Ignore any other messages that appear in the Terminal window.
The application window will open, eventually showing all files in all folders, sorted by size. It may take a few minutes for the app to finish scanning.
I don't recommend that you make a habit of doing this. Don't delete anything as root. If something needs to be deleted, make sure you know what it is and how it got there, and then delete it by other, safer, means. When in doubt, leave it alone or ask for guidance.
When you're done with the app, quit it and also quit Terminal.