[support] CSS lost for anonymous users

On further testing my new module I discovered that all the styling disappears for anonymous users. This is drupal 6. What makes it more interesting and more difficult to debug is this does not happen on my development box, only on the production server. In looking into this I've noted that this behaviour is not unknown but those instances I've read about have little in common with mine.

Any thoughts on what I should look for? I've gone ahead and moved the module style sheet into the theme directory so all appears okay now but I'd like the module to be stand alone as I've submitted it for consideration to the drupal community.

Thanks