"The document 'Backup of Backup of Oral Report' could not be saved as 'Oral Report'. Bad file descriptor"

Hello,

Whenever I try to save my Keynote file, I receive an error message saying: "The document 'Backup of Backup of Oral Report' could not be saved as 'Oral Report'. Bad file descriptor".

I've tried using other name to save my file, saving the file as a backup, saving it within my documents, and on a USB, but the file won't save. I'm using Keynote '09, Version 5.1.1 (1034) on my Mac Desktop running Mac OS X Version 10.6.8

How can I fix this problem and save my file?