This is the only support forum post I've seen remotely close to what we have going on.

Currently we have a client who has a 2 workstation setup.  One workstation hosting the company file, the other just accessing in multi-user mode.

In order for the second system (the one not hosting the file) to access QB, the hosting workstation must close QB, then and only then can the second system log in, follow by the hosting system.

To break it down, if system 1 has the company file open, the second system cannot access at all until the first system closes.

We tried all the normal troubleshooting steps and even talked to level 2 support.  They have not been able to come up with a solution.  Our client continues to be upset, since this has been going on for 6 months +.

Support is blaming the firewall, but when I explain to them that it works if system 2 opens first, it blows their minds.

I'm not sure issues posted here are not file corruption or actual software problems. Getting a developer or an actual technician who can assist or understand is impossible.

Please do not reply with links to check hosting, ini, services, file doctor, or any other thing you can google for answers. The software is broke. QB support doesn't seem to care, even with a support contract. 

Take a look at the error we get without an Error code (attachment). If the company file is opened by system 1 first and system 2 tries to open it.