In my very new, lab install of SharePoint 2013 in Windows 2012, I get this error message when trying to post to the newsfeed

SharePoint returned the following error:

> 
> Unexpected response from
>  server. The status code of response is '500'. The status text of
>  response is 'System.ServiceModel.ServiceActivationException'. Contact
>  your system administrator for help in resolving this problem.
> 
> 
> 

So far, I have: 

* Checked that the `ASPNetCompatibilityEnabled = true`
* Checked the memory (50% free memory).
* Changed performance level (`Set-SPEnterpriseSearchService -PerformanceLevel Reduced` as mentioned [here](http://sharepointthing.wordpress.com/2012/11/18/sharepoint-2013-unexpected-response-from-server-the-status-code-of-response-is-500-the-status-text-of-response-is-system-servicemodel-serviceactivationexception/).
* Disabled MDS (`Disable-SPFeature -Identity 87294C72-F260-42f3-A41B-981A2FFCE37A -Url XXX`).

Those changes haven't helped.