Backup 3 may unexpectedly quit if essential applications are missing

Backup 3.0.x may unexpectedly quit if certain essential system applications are missing or have been renamed.

This issue may occur if any of the following system utilities are missing from their standard location:
du
hdiutil
gzip

These files are normally invisible. If Backup is unexpectedly quitting when you try to use it, look for the files and make sure they're there:

1. From the Go menu, select Go to Folder.
2. In the window that appears, type the following exactly as it appears below:
   /usr/bin/
3. Click on Go.

The folder should appear in a new window, displaying its contents. If any of the above files are missing, reinstall Mac OS X.