Try turning off protected mode.
That solved the issue. Many thanks.
Disable Protected Mode by going to Edit > Preferences > General and deselecting Enable Protected Mode at startup.
Is there any way to set preferences in Acrobat that will make it unnecessary for others trying to submit the fdf file using Reader X from having to change the default setting for the protected mode?
Many thanks again.
No. Acrobat can't influence the Protected Mode setting in Reader.
This was happening to me with a form I created in acrobat Pro X and was testing using Reader X (accessing the fillable form from the internet so I want to make sure people can use it) for submitting. This general preference change fixed my problem but I can't fix it for all the visitors on my website (no way to set this in the form itself after it is opened?) I can get the file to attach and create an email but only if I leave off the email address (I just enter 'mailto:' in the URL). Please let me know if anyone out there has a possible solution that will work for the web - I have an order form that can be filled out online.