Error adding Custom Command item to VSIX project

creating an Extension with a Menu Command. Getting error when I add a custom command item template.  Error message is "cannot find file key.snk".

I first create the project. Extensibility, VSIX project. Then add item to the project, extensibility, custom command.  Wizard runs for a while. Then the error message: "cannot find file ... key.snk" 

Then I try to add the key.snk file to the project manually.  Project properties, signing tab. Check the sign the assembly box. <New> file name. Enter key file name key.snk. Uncheck protect with password.  Get the message: "the operation could not be completed.  Access is denied." 

Why this error?  When I run visual studio "as administrator" I do not get this error.

thanks,