Metadata keywords remain after I delete them

I am creating a diagnostic tool for PDFs, and one of my flags is whether the document has metadata, specifically keywords.  My output from the diagnostic tool is a tab delimited file.  I use the following Javascript to report the keywords of the PDF.

dataLine += this.info.keywords;

The issue is that when I manually delete text from the keywords field, save the file, close it, reopen it, and then run this script, the output is the exact text that I just deleted.  Why is the output not blank?  The document properties show nothing in the keywords field.

For instance, if I type into the keywords field "test" and nothing else, save the file, close it, reopen it, and then run this script, the output is "test", as expected.  Now when I manually delete "test" from the keywords field, save the file, close it, reopen it, and then run this script, the output is still "test".  I would expect the output to be blank, not "test". 

What has not worked is deleting the cached file that stores all the text that I typed into the metadata fields.(C:\Users\cboccio\AppData\Roaming\Adobe\XMP\FileInfoLibPrefs.txt)

I am using Adobe Acrobat XI and I can post the entire script if that would be helpful.

Any ideas are appreciated.

Thanks,

Chris