Hi justinanmartin,
I'm happy to shed some light on what's going on.
When switching from Multi-User mode to Single-User mode, the Host computer puts out a signal for your second computer to work off of. When you break that line, the only way to get it back is to restart the program.
I'm attaching an image below that represents the connection between the Hosting device and the secondary workstation:
You might also consider reading this handy article that will discuss you more about access limits in single or multi-user mode: Tasks that can be performed in a single or multi-user mode in QuickBooks Desktop.
Stay in touch with on how everything goes, justinanmartin. I'll be around to help.