We are aware of an issue that is currently affecting Chivalry: Medieval Warfare players using the Steam Client Beta.
Opening the server browser in Chivalry: Medieval Warfare while using the Steam Client Beta may result in a crash.
For information on how to opt in/out of the Steam Client Beta see https://developer.valvesoftware.com/wiki/Betas#Joining_a_Beta_test
Edit: the issue has been resolved. The Chivalry server browser now works correctly in the Steam Client Beta.