Grabbing this file: http://www.irs.gov/pub/irs-pdf/i1040tt.pdf, and opening it in Acrobat Pro XI, it worked for me just now.
Computer issue? Reboot? Reinstall Acrobat Pro? Try on a different computer?
I was also able to convert the same one you did. Attached are the two documents I could not convert to word. Can you see if it works for you?
Thank you Brian,
You can't send attachments through the Adobe Communities chat system. Can you send links to the files in question?