This section explains how to deal with an installation that reads, "Your administrator has blocked this application because it potentially poses a security risk to your computer." Complete details on this error and the solution can be found here, on Microsoft's web site. Follow the instructions under the "Enabling the Click Once Trust Prompt" heading. Condensed instructions are shown below.
Installation Error
Enabling the ClickOnce Trust Prompt
Enable the trust prompt for a zone when you want end users to be presented with the option of installing and running any ClickOnce application that comes from that zone.