Nonce Field

I am using the plupload flash uploader to upload files in a plugin. I am trying to use a nonce to secure this. However, when I send the nonce, it does not validate. It thinks the ajax call from the flash uploader is coming from a 3rd party source or something. Anyone know a way around this? Guess it is not a huge deal since the uploader is only accessible from the admin panel, but would still like it to be more secure.

Thanks.