I also have the retail disk origin install and the trainers I've tried them all do not work for me, I also read the read me's and have done all the items on the faq, compatibility etc and I have not been able to get them to work. I've tried all the retail/origin trainers posted.
I've also used dozens of other trainers here without issues. Must be something related to the retail install when using it through origin.
V
Really strange. I also have the retail disk I installed from and the first steam/retail trainer from here (dated 2-06) is working fine for me. I know there was no download involved in my installation since I was at the computer during the install. I know there was no update done on the game when running it the first time (yet). Wish I could be more helpful to those like me with the retail disk who are having problems.