It happens when the server and your client are out of sync, was used as a cheap way to pick up speed cheats, the client would run faster than the server and give code 10k.
Looking at the code for it, theres a few possibilities, some more likely than others.
- You have tweaked your computer and/or it is generally fast, it runs the client faster than normal causing your client and the server to go out of sync
- Your computer can sometimes be too slow, not really very likely as mir is a very old game and doesn't take much to run.
- You are running some form of OS speeder, speeding up your operating system, some of these get around code 10k, some don't.
- Server is extremely laggy, doesn't look likely from your screenshot as nothing is going on.