I get it all the time. It has to do with ESKO plug-ins that we use with illustrator. Can't get rid of it. Tried.
I do get this message quiet a lot!
it is at most annoying, although I get the added problem in that after I have had this message the file will fail to print until i close down the file and re open it again!!
Any suggestions most welcome??
BTW I am saving to a shared Network drive if this makes a difference, although no one else is using the file or indeed illustrator.
You have probably opened the file in Acrobat and modified something or have a linked file say a .psd place in the document and it was altered
without updating it in Illy.