I keep on getting this error. I tried one solution from stackoverflow (below) which did not work for me - SQL Exception while connecting to SQL server
I tried allow
Steps
Open the Sql Server Configuration Manager (Start -> Programs -> Microsoft SQL Server 2008 -> Configuration Tools)
Expand SQL Server Network Configuration -> [Your Server Instance]
Double click TCP/IP
Under Protocol:
Ensure Enabled is Yes
Under IP Addresses:
Scroll to the bottom and set the TCP Port under IPAll, (1433 by default)
Find the IP address you want to connect to and set Enabled and Active to Yes