I have a problem On a XP system with SP2 installed and using IE6

If I try to upload a file for validation at the w3c validation service http://validator.w3.org it refuses to validate it saying the content is text/plain.
f I use Mozilla Firefox on the same PC, then there is no problem and the validator works.

I have tried it on a PC WITHOUT Sp2 and it works fine on both browsers.

Can anyone point me in the direction to a solution. I need to validate files using upoload as they are not yet deployed on a web server and we use IE6 by default.

The actual message displayed by the validation service is
Sorry, I am unable to validate this document because its content type is text/plain, which is not currently supported by this service.

The Content-Type field is sent by your web server (or web browser if you use the file upload interface) and depends on its configuration. Commonly, web servers will have a mapping of filename extensions (such as ".html") to MIME Content-Type values (such as text/html).

That you recieved this message can mean that your server is not configured correctly, that your file does not have the correct filename extension, or that you are attempting to validate a file type that we do not support yet. In the latter case you should let us know that you need us to support that content type (please include all relevant details, including the URL to the standards document defining the content type) using the instructions on the Feedback Page.