Can't apply redaction! Problem reading this document (16) Acrobat 9 pro

I am trying to apply redactions to sensitve data. I go through all the steps, mark it for reaction etc.. but when I click to "apply redaction", I get the error message "There was a problem reading this document (16). I can't find an answer to this anywhere!

The file I'm using originated from a CD sent to me from our retirement administrators. There are no restrictions on what I can do with the files.

I've tried this on 3 different computers, using both Acrobat 9 Pro (with most current updates) and Acrobat 10 Pro and I always get the same error message. Even when I extract one page, rename it and try to manually redact (without using search and redact), I still get the same message.

Any ideas???  I really need to redact social security numbers!

Thanks

I'm using windows 7 pro if that helps...