Alright, after trying a few things I finally gave up.
My login screen (after running the Launcher) is black.
This happened today, I could login yesterday without any problems.

http://i.imgur.com/aQ1oL.png

And either after waiting a minute or when closing the window this message shows up:

http://i.imgur.com/QZ5Av.png
"The launcher has experienced an error. Please restart this application."
It would be nice to know what's the actual error.

(Why? Why did the developers use Internet Explorer to display web content?)

Music is playing and it seems to be doing something, the mouse lags at some places.
I'm on Windows XP and still have the Internet Explorer 6. I'm definitely not going to install the new one.
I've also already tried repairing LoL using the installer, redownloading it by removing the lol-cb3.game.version file, resetting the internet settings and running Microsoft FixIt. I have the lastest Windows update.

I found a lot of similar threads on these forums, but I couldn't find the solution to this.

So ... is it possible to fix this at all or is there more information on this?
Thanks in advance for the help.


EDIT: I just noticed the .log files and in maestro-server.log there is this line which shows up (multiple times) when the error does.

I'd say updating your Air will solve the problem. If not try reinstalling or downloading Matric' client and see if it works better.

I just remembered. The first time I started LoL today was using a program I wrote myself, which simply runs the launcher, but the current directory wasn't the game's directory. I'm currently installing the game another time after I deinstalled it completely.
I'll report the problem/error once I find it.

Updating Air didn't help.
Maybe the ports Maestro uses are blocked ...

EDIT: Aaaand for some reason it works now.
What did we learn? Reinstalling solves problems. So nothing, really.
*sigh*