The Acrobat/Reader stamp file specification has not changed sinced Acrobat/Reader 6. So if the stamped worked in an earlier verion it will work in Acrobat 9 and later as well. Since she recreated the stamp it is very likely that she did something different, because it sounds like the stamp was made incorrectly.
Not all pages in the stamp file are stamps. Stamp pages are marked in a special way. You typically make a dynamic stamp by first creating a static stamp, and then manually modifying that static stamp. So, did she create a static stamp first? and does this static stamp show up where it should on the stamp menus? This is the starting point for a dynamic stamp, and the first thing that should be checked before adding dynamic features to the stamp file. See the link below for the "All About PDF Stamps" book. You'll find everything you need to know about creating stamps there.
BTW: it is not a good idea to add new custom stamps to the built-in stamps, and especially if it means editing the original built-in dynamic stamp file. It is much better to create your own stamp categories.
You also need to restart Acrobat after creating the dynamic stamp file.
Thom Parker
The source for PDF Scripting Info pdfscripting.com
All About PDF Stamps in Acrobat and Paperless Workflows - THE BOOK!
The Acrobat JavaScript Reference, Use it Early and Often
Then most important JavaScript Development tool in Acrobat
The Console Window (Video tutorial)
The Console Window(article)
Having trouble, Why Doesn't my Script Work?
