Lol, suspicions were right.
Gets past the initial loading screen every time with the mechanical HDD. It's almost as if the content loads before the actual loading screen comes up when its off the SSD, therefore the game misses the trigger to continue onto the main menu.
It's not a crash to desktop, it's just that the loading screen gets stuck into an infinite loop and never actually progresses past it.
I'll get a video recorded in a bit to show what I mean, but if im right then this could become a common problem with fast SSD's!
Ive had this a couple of times (stuck on loading screen in a loop)
Using Velociraptor 150gb drive