1 - initialize normaly click play ( not work )
2 - END process Blizzard launcher
3 - initialize again ( then stuck at 0% )
4 - END process agent.exe
5 - HAVE FUN
enhj0rning, a big thank you. That resolved my problem. I had tried most combinations of killing agent.exe and Blizzard launcher but not that one. Worked a treat.
Imagine my horror though when, after a day of not being able to get the game even launched, I got error 37 the first time I tried to login (first time I've seen that so far). Thankfully I was able to login the second attempt.
Gotta give a stickied to this !!