SQL - an error occurred during the pre-login handshake

Solution 1:

An answer propsed here: http://social.msdn.microsoft.com/Forums/en-US/vssetup/thread/2d11b6f9-3ada-4682-b643-c721a97af4ba

Sick of the problem? Dont know or care what winsock is or any of this low level crap means.

Go to a command prompt

do this

netsh Winsock reset

go on with your life and be happy.

Solution 2:

In my situation, I had a content filter/proxy called Covenant Eyes that was the likely cause.

I tried repairing the install of SQL server 2012 and it crashed the install and still did not fix the problem. As soon as I generated an uninstall code and uninstalled the filter, I could connect; I did not even have to reboot.

Check for proxies and content filters on the machine and disable them!

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Solution 3:

In my particular setup, I was using storing session data in a custom database, I also had the data encrypted (Encrypt=True) via the connection string, removing this fixed the problem!

I suspect though that the data isn't being ssl encrypted as a result though, not much of an issue until we add more web servers though!