The issue you are having is not related to RadControls but to the inability to make a connection to your SQL server. There are number of possible reasons that could cause this behavior. For example:
- The SQL Server itself is not running.
- The server or instance name are misspelled
- You are connecting from a remote machine, and there is a firewall in the way.
I can suggest you to examine this
blog post and this
forum thread on the matter or make a research on the internet about the issue.
the Telerik team
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