Premising that I still cannot do any test because my S2 hasn't arrived yet, try looking at this.
It seems to be related to a specified user, maybe you can try log in with ssh and create a new user, just to see if it works.
Make sure that all paths in the bootbt script are correct, I've seen that for other devices they have changed some.
Also that could be useful.
Found a fix here.
Keep me updated, I'm interested in this too!