Acrobat Pro 7.1.0 and Mac OS X 10.4.11
This problem has been plaguing me for days, so I'm documenting it here in case someone else gets hit with it.
I've been modifying a Preflight Profile (based on Sheet offset) for our own purposes. I change some of the settings, run a few test PDFs, do some more modifications, retest, etc. This all occurs in spare time over a couple of days. Once I get it just right I give it a final name and write comments about its purpose.
Next time I open Acrobat and the Preflight window I get this error and my lovely new profile is deleted from the list GONE. So, I have to start again.... (I couldn't find a way to resurrect the .kfg file as I didn't know which line of code was the issue)
After much frustration I found that extra line breaks in the "Purpose" text field cause the profile to be considered 'invalid'. Of course, there's no warning that the profile will become invalid the first you know of it is the next time you start up Acrobat.
Hope this helps someone else.
d.