Your question is not about FormsCentral. I suggest you to check whether Adobe Reader is enabled on your web browser's add-in list. For example, on Chrome you may type in "chrome://plugins/" to open the Plug-ins list, and check the status of Adobe Reader. If it's not the latest version, you may update it as well.
You may go to Adobe Reader's forums and start a discussion if you like: http://forums.adobe.com/community/adobe_reader_forums