I just spent a couple of hours fruitlessly trying to solve a problem and thought I’d blog the solution in case anyone else hits the issue.

A few months back I got a new laptop and installed SQL Server 2014 on it and everything worked fine. A few weeks ago I installed SQL Server 2008 R2, SQL Server 2012, and Visual Studio 2013. After that, any time I tried to use the Dedicated Admin Connection (DAC) through SSMS, I got this error:


I did some research online and couldn’t find any solutions that worked. So I tried repairing the installation, installing 2014 SP1 CU2 (latest build at time of writing), and a bunch of other things – to no avail. I was just about to give up and post a request for help when I thought I’d do one more search online.

When I did that, I noticed that all the solutions I’d tried had revolved around the assembly name in the error being something to do with SQL Server. In my case, it was System.Data, which is a .NET assembly. I added that into my search and found a bunch of new hits. Lo and behold, buried in the comments on a Stack Overflow question, I found the solution.

Turns out the problem was because of an upgraded .NET version, and the solution was to run the following from a command line and then reboot:

netsh winsock reset

And after that SSMS worked perfectly.

Hope this post helps others find the answer quickly in future!