I get this 404 error when it's customizing my download. Since the other trainer downloads work I assume it's due to the transfer, but thought you'd just like to get some more information on this just in case.
That would certainly make sense. I tried a different browser earlier for that trainer and it worked, but then using that same browser a different one gave me a 404 at the same stage. I usually use Chrome, which seems to be fine now, but if it's sporadic (I'm glad I'm not the only one) than it's most likely what they're doing.