If you can't add attachments to Gmail messages then you need to add an allow exception to allow pop-ups for that Google website. Easiest to do this is to click the padlock on the location bar and click the "More Information" button to open the "Tools > Page Info" window with the Security tab selected. Proceed to the Permissions tab Remove the tick on "Open Pop-up Windows" > "Use Default" and click the Allow radio button to change the permission to allow pop-ups for this domain. Google is looking into this issue, see: * https://productforums.google.com/forum/#!topic/gmail/q0BxcGOa6pk