I am working on deploying a ClickOnce Application build on .NET 4.5 Here are the facts:
First you must publish to a website in IIS not a UNC path. Publish to the folder the site is pointing to.
Second import the certificate into the Trusted Root Certificate Authorities Folder on MMC console.
And then finally when signing the manifest choose Select From Store on the Signing Tab in Visual Studio. I got this to work with a Test Certificate.
I hope it helps.
Thanks