I have exactly the same problem as Morfineth. I was a long-time LOTRO player until I moved on 6 or 7 years ago. I read about Treebeard and decided I'd like to give it another go through the progression experience. I restored my VIP subscription, downloaded the game, created a new character on Treebeard, but then when I hit the button to enter the game I got to the loading screen, the loading indicator ring pulsed exactly once, and then the screen froze. I have tried every published trick I could find, to no avail. I uninstalled and reinstalled the game several times, both from the Standing Stones download site and from Steam. Every time, the exact same result. I even downloaded the game on my lowish-end laptop on WiFi, and it actually worked. I got into the game, but because of the inferior hardware and connection it wasn't particularly playable.
My best guess is that there is some kind of hardware (or maybe software) incompatibility with my new desktop system, which is a high-end Alienware rig with the latest GPU. I did put in a ticket last week, but have not heard anything back yet. I'm going to make one more download attempt and then just give up. I guess I should not have renewed my subscription until after making sure I could get back into the game, but it never occurred to me that with my new system it would be a problem.
The generation of random numbers is too important to be left to chance.