Backup Failure after Mountain Lion

Question

After I upgraded to Mountain Lion I got an error every time I tried to backup over wireless. I figured I would just backup from scratch, therefore I connected the hard drive to my USB, deleted the sparsbundle and then connected the hard drive back up to the Airport Extreme.
Now every time I try to backup wirelessly I get these errors (using Time Machine Buddy):
Starting manual backup
Attempting to mount network destination URL: afp://**********;AUTH=SRP@****%20******._afpovertcp._tcp.local/Time%20Machine
Mounted network destination at mount point: /Volumes/Time Machine using URL: afp://**********;AUTH=SRP@****%20******._afpovertcp._tcp.local/Time%20Machine
Creating disk image /Volumes/Time Machine/*****.sparsebundle
Error 60 creating backup disk image
Failed to create disk image /Volumes/Time Machine/*****.sparsebundle, status: 60
Backup failed with error: 20
Ejected Time Machine network volume.
My setup is an airport extreme base station with a Western Digital Drive connected to it. Of note, two other computers (both Lion) backup to this drive wirelessly via time machine and continue to do so flawlesly.
Please help discussion board, you're my only hope!

Answer 1

First, empty the Trash if you haven't already done so.
Use a tool such as OmniDiskSweeper to explore your volume and find out what's taking up the space.
Proceed further only if the problem hasn't been solved.
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 really see everything, you have to run it as root.
Back up all data now if you haven't already done so. No matter what happens, you should be able to restore your system to the state it was in at the time of that backup.
Launch the 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 page that opens.
After installing ODS in the Applications folder, drag or copy — do not type — the following line into the Terminal window, then press return:
sudo /Applications/OmniDiskSweeper.app/Contents/MacOS/OmniDiskSweeper
You'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up.
I don't recommend that you make a habit of this. Don't delete anything while running ODS as root. When you're done with it, quit it and also quit Terminal.