I work for a company that distributes e-books in PDF format using Adobe Content Server. Some of our customers keep getting the above error since we upgraded to ACS4. I've looked at the technote, but it didn't really answer my question of why this happens, since:
a) We have upgraded to ACS4, yet our server seems to still be sending out ebx.etd files occasionally rather than urllink.acsm.
b) It doesn't happen all the time, unlike what the technote says; the same ebx.etd file that gives a customer the above error works fine for us when we download an e-book on a separate computer.
So I suppose my question is, is there any other problem that could cause this error message?