My field names are missing too....
Might Adobe Acrobat Pro version 9 be installed on this computer?
For More Information see: http://forums.filemaker.com/posts/1dd95f9381?page=1
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip