To fix this problem we added opacity:1 !important; and on the cxsFileupload frame we have changed the opacity to 0. This must be 0 because otherwise our button will be shown on application forms of customers that use their own document upload button(s). That is why it was necessary to hide it.
We recommend the web administrator to create the document upload button(s).
Click here for our style sheet. From .cxsButton ,.cxsFileUpload up to and including span.cxsFileUpload you can see how we created the button.