I had this three times in a row today. I join a friend's server via the steam-overlay while already in the main menu of DayZ Standalone.
Once I'm in the server, my controls freeze up and I can't move either with keys or mouse, and also not access any menu since the ESC key also doesn't work.
The only way I can get out is by shutting down the game.
After several attempts I joined my friend's server directly from Steam without having started DayZ. This solved the problem.
Start DayZ, wait for main menu to load
Activate steam overlay (Shift+Tab)
Find a friend who is in game
Join friend's server
Wait for server to finish loading and character to spawn in
I initially thought this may have to do with me using the steam overlay while getting into the game so that my map is up and loaded. However, the third attempt I did absolutely nothing except StR - same result.
Hello ColonelBurton,
In this case I would recommend that you contact Steam's support in order to pinpoint why the Steam overlay makes the game freeze: https://support.steampowered.com/
Regards,
JStewart