Problem with CSS style sheets when uploading a theme

Hi,

I’ve recently signed up to a webiste called elegant themes, I choose my theme and tried to download. BUT!! every time I download and then instal the theme on WP I get the following message;

Installing Theme from uploaded file: Chameleon.zip.download.zip

Unpacking the package…

Installing the theme…

The package could not be installed. The theme is missing the style.css stylesheet.

Theme install failed.

I’m unsure why this happens. The themes provider said it could be me using a mac with safari?

Any help is appreciated.