CSS Validator Inconsistent Behavior

When I paste in the css text below to the text area of the CSS validator 
(http://jigsaw.w3.org/css-validator), I get different results upon 
multiple submissions.  Sometimes it validates just fine, but sometimes 
it comes up with a warning stating 'This property applies to block-level 
elements'.  Screenshots of both warning and no warning have been attached.

Here is the css:

..image {
     text-align : center;
}

My guess would be that there are multiple servers running the validator 
that are not running with the same code and/or configuration.

Any assistance would be greatly appreciated.

Thanks!

Ryan