When I installed .net 4.5.1 on my windows server 2012 (version 6.2 build 9200), all sql server connections were broken. Any time I tried to connect to the sql server, I'd see an error stating:

The message received was unexpected or badly formatted.

I also saw this C++ runtime error in some programs like linqpad and SSMS:

r6025 pure virtual function call

This caused app pools in IIS to completely stop for any site connecting to sql server.

When I finally uninstalled .net 4.5.1, connectivity to sql server was restored, but applications requiring that version of .net fx were out of commission.

Google and event logs haven't turned up anything useful for how I should proceed to get .net 4.5.1 on this machine.

Any ideas?


I had the same issue on windows 7 Enterprise SP1. Upgrading .NET to 4.5.2 solved it for me.

Found the solution in this post - which points to this MS KB.

I realize this is an old thread, but it was one of the top search results for me - hopefully it can help someone else.


From this post


netsh winsock reset

  • Tried that the night before. Seemed to work, but the next morning things were broken again. – Ronnie Overby Jan 7 '14 at 1:08

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