Go to the SQL Configuration Manager. (You can refer to the link above for a walk through with screen shots to get there)
Expand the SQL Network Configuration and click on the PROTOCOLS node
Right click on TCP/IP and open up the PROPERTIES panel
Select the IP ADDRESS tab
Make sure the values for the IP ADDRESS fields are correct and match the system it is running on.
Restart the service, and you should be back in business, I was.
On a side note, this is also the same place where lots of people get hung up when setting up remote access to a SQL Server instance.
Make sure you fill in the TCP PORT, even if you are using the default 1433.
7. Now extract and you should have your content without any errors out of RAR files.
If you are still experiencing the issue you can try SQL Server Fix Toolbox