Steam “not responding” on iMac 5k

Question

I've just installed the Steam installer on my new iMac 5k, and downloaded the latest version of Steam onto it. When loading Steam, the login window loads, but all of a sudden the application freezes and needs to be "Force Quit". Any thoughts what a solution to this might be?

Answer 1

Ok, so I've managed to figure out a solution:

1. Uninstall Steam
2. Turn off the computer
3. Turn on under "Safe mode" (more info here: http://support.apple.com/en-us/HT201262)
4. Download and install Steam under Safe Mode
5. Once installed launch, enter login details, and close Steam
6. Restart the computer as normal, and Steam should be working just fine

Enjoy :)

Answer 2

Try disabling firewall in Security & Privacy settings, try adding rule to accept all internet traffic for desired application in Firewall Options.

When I start steam the first time of the day it crashes due error you describe, when I start steam 2nd time everything works just fine.