I was experiencing this issue too. I cannot type in guild chat and I cannot open the Guild&Social window (Default is J). I can disable all addons and reload the game and I still cannot type in guild chat and I cannot open the social tab.
After closing wow completely (not just relog), and reopening wow about 2 or 3 times I got the social window to open and I could talk in guild chat. I then renabled my addons and I was still ok. So I restarted wow and once again could not open social window or talk in guild chat. Leaving my addons on, I closed the game and relaunched with my addons enabled until the social window and guild chat was available to me.
I can also repeat this while having no addons loaded. This behavior occurs regardless of addons I have. With 0 addons, I can relog and social breaks. I can reload again a few times and eventually social comes back.