So I got this today: error MSB3482: SignTool reported an error ‘Keyset does not exist’. I was trying to publish a project in Visual Studio 2005. Here is the resolution:
Right click the ClickOnce key marked with the PFX extension in your projects folder, install it and try to publish again.
The cause apparently was that I changed the configuration of the compiling. Changing them back to the original state did not work because the damage was done.
Let me know if this helps!