Steps to reproduce:
On Windows:
1. Install/Activate "Unity 5.3.0f1" with "Unity 5.1.2f1 Cluster Rendering build" beta key
2. Download and open attached project "repro_738382.zip"
3. Build for "Linux x86_64" and don't forget to include scene Wall2x2.unity (For convenience, build the file with name "demo")

On Linux:
1. Launch the built demo as a server, by executing "server.bat" file (attached)
(Note: If more than four digit port numbers are used, it crashes right here - different, known, bug)
PROCEED WITH CAUTION
2. Launch another demo instance as a client, by executing "client1.bat" file (attached). Notice that it crashes/freezes. On multiple instances I had to reset my Desktop Environment and/or reinstall GPU drivers (cannot confirm if this is related to the crash)

Expected result: Nothing crashes/stalls and I can control clients from server instance.

Build tested and reproducible on:
Windows 10 w/ Unity versions - 5.3.0b3, 5.3.0f1, 5.4.0a2
Launching tested and reproducible on:
Ubuntu 14.05

Not reproducible w/ 5.1.2f1 (Cluster Rendering build)