We are displaying attachments with a specific label on a page.

When browsing for an attachment and add to the page, the page thinks, and then gives an error: Error occurred. When we close the error message, the page refreshes and the attachment is then there (and labeled).
We don't want to use the drag and drop functionality because we don't want users having to do the extra step of labeling.
Any idea why we are getting the error message when using the browse functionality?