So, I was forced onto the new beta (14.0.8015 so on), and I'm having troubles.
Since I upgraded to it (Thursday night) I have only gotten the 8000401a error all the time.
I tried out a couple of things from the previous threads about this, without much success (like these http://ugosan.spaces.live.com/blog/cns!49B4220E95DBBA3D!5999.entry Apparently option 2 works pretty well for others, but it says it can't get access to the registry or something when I try to add it)

Something changed though, because now it tries to sign on, at least. Before it instantly gave me the error.
But it just says "signing in" all the time. I've had it on or like 15 minutes, still just "signing in".

Any clues how to fix this?

(I use Windows XP, SP2)

Download the final version.

I have that. At least I got it from download.live.com, so I'd expect it to be final.