Error Code 51

[andrew5879]

Whenever I try to run it through steam I get error code 51
Searched around and this is a networking/firewall problem, but adding steam and amnesia as exceptions didn't work.

Anyone had this problem or have any understanding of how to fix it?
I'm using Avast

[Mudbill]

https://support.steampowered.com/kb_arti...-SFLZ-9289
You might have already read this, but it will be of good reference. It seems 51 can be caused by interfering background programs, so try to shut down a few. Perhaps a hidden process is causing it in this case.