Version: Steam Client Beta - June 5th

Issue: This update crashes both Steam and Arma 3 to desktop when entering/exiting Zeus.

Replication:

Open Arma 3
Become Zeus
Do Zeus things, enter and exit camera etc.
It will crash, sometimes not immediately but it will.
Both Arma 3 and Steam fully crash causing you to have to restart steam completely.

It does sound really odd but this seems to be the problem, I've had this issue for a few days.
Using this thread on reddit a comment suggested switching off the beta client.

https://www.reddit.com/r/arma/comments/1tzchev/arma_3_game_and_steam_crashes_after_leaving_zeus/

All of my issues stopped the moment I switched back to the non-beta client.