Q: I'm having trouble backing up my iPad.  I get a message that reads, "iTunes could not back up the iPad because the backup could not be saved on the computer.

Try to delete the MobileSync/Backup folder, see this document:

http://support.apple.com/kb/TS2529?viewlocale=en_US&locale=en_US

The folder is in your User Library, and that is hidden by default:

~/Library/Application Support/MobileSync/Backup/

To find the ~/Library folder on OS X Lion v10.7 or later, hold the Option key and choose Go > Library.

That will open a Finder window for the hidden User Library. Open the folder Applications Support, then the subfolder MobileSync, then Backup.