File Upload does not work when theme is change from default

This is a starnge one. My file upload worked then suddenly didn't - the only thing that I could think I changed was the Theme.

Sure enough if I changed the theme back to default and file upload worked again.

Has anyone else got this problem and anyone found a work around - I would like to use the AZUL theme.

Still cannot upload a company logo even with the default theme though.

Thanks