Possible CSS Validator bug

Hey!

Can you please explain me, what does this error-message mean?
Screenshot is available here:
http://taimar.pri.ee/temp/invalid_byte.png

This page validated ~2 months ago,
but now it's mysteriously broken.
And I havent edited this document meanwihle.
HTML Validator gives *no* warning/error whatsoever.

Could you please tell me, what has been changed in CSS Validator and why?

Best regards,
Taimar