well ken, there's your problem, as long as you cannot click the "submit reply" button on that very page the attachments will be discarded.
unfortunately that means, this is a user-side issue;
namely your browser/device your using this site with.
AS long as we don't know these details (device, browser, version where applicable)
we cannot help you solve that issue.
PC, Mac or mobile device(any ios or android tablet or phone)?
what browser are you using (internetExplorer, Firefox, Chrome, Opera, Safari or any inbuild derivate safari or chromium based)
check the settings to allow opening links in new tabs (important to not close the actual posting tab)
check your settings, and/or tell us about your device so that we can figure it out for you.
'sid