Validator output doesn't validate

Hello. I use the firefox web-developer toolbar along with the shortcut
ctrl+shift+a to post the current page to the validator.

I noticed that in one case, the output of the validator was itself
invalid. Here is what I did:

1) I visited http://www.ddna.org/
2) hit ctrl+shift+a
Came up valid
3) Hit ctrl+shift+a again on the w3.org validation results page


Thanks
-Michael