This error is due to referencing one or more assemblies that were downloaded from the web and perhaps extracted from a ZIP file - things such as third party controls. These assembly files have a "block" flag set on them for security. I have found couple of way to resolve this error.
1. Disabling the blocking property of an assemblies for which you have to locate that particular assembly in Windows Explorer and right clicking will open its Properties where you have to click on the "Unblock" button placed on General Tab.
2. Disabling the security check permanently in the Visual Studio 2010. Open the config file located at " %ProgramFiles%\Microsoft Visual Studio 10.0\Common7\IDE\devenv.exe.config " then add the following code under the <CONFIGURATION> element:
Code:
<runtime>
<loadFromRemoteSources enabled="true" />
</runtime>
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