Can’t register new user

I'm running SQL version on SLQ Server 2000. I can log in OK using the admin id, but after logging out and attempting to register as a new user I get two problems:

1. Occasionally the security code images do not show up, i.e. they show as red 'X'es. A reload usually takes care of this.

2. After filling in the form, I hit the Register button and it goes to the "insufficient permissions" page. I have not locked the forums.

Any suggestions?

Well, I guess that's the problem. We are using two load-balanced servers.

How do I make sure that the session is not dropped? The servers are supposed to be configured so that (for a given session) only one computer responds to a given user, but obviously this is not the case. I've configured the forum as an application with sessions enabled. What else do I need to do?