I'm also having this issue and i'm sure it's related to users not being able to switch to multi-user mode. They receive the H202 error when they try. I'll scan the company files on database manager and receive that error "windows firewall is blocking quickbooks". I've manually configured the firewall based off the article listed above but i still receive the message. File doctor says everything is okay on both my server and client computers. Also, the only way a user can switch to multi-user mode is if the company file is already open as multi-user mode on the server. I've called quickbooks a few times but we have not been able to get this going. The only thing i havent done is reset windows firewall back to factory settings but that's something i really dont want to resort to.