Question according to Google Translate:
I downloaded some of the things that Web page (for the download button), press only the pop-up download downloadattachment.php, rather than the original files, but other browsers can.
After updating FIREFOX

If you get downloadattachment.php for every download instead of the original files after updating to Firefox 8 then the server is probably sending an illegal Content-Disposition header. In Firefox 8 this is no longer allowed and the filename will not be recognized.
For example if the server sends:
Content-Disposition: attachment; filename*="ABC.doc"
This is working in Firefox 7, but it is not working in Firefox 8 and the server needs to be fixed.

not every file be downloadattachment.php , but some file be. (now, i used firefox7,so now is ok)So, i hope mozilla company can deal with this problem(firefox8).Thankyou