I'm really not sure you're using the right script. b2evo really wasn't designed to handle that many users. To make b2evo easy to use with that many users, you'll have to make some pretty extreme modifications.

what, do you call that many users?? I don't understand you, it's just some few users... well I'll have to modify user administration a little then.... :D realy weird... it says multiuser, and when I got some few users... hmmm.... many users is 10000+ I think...
extreme modifications, nonono, not for me...

ehrmm... can you recommend another free system or should I rewrite that little part?

(got it running with the same auth system as Phorum to :D that was just to easy to do...)

1100 is a lot of users for a blog. Maybe not for a forum, but b2evo isn't a forum.

I agree that you'd be better off with using a different script as a portal.