I\'m signing an EXE program with a certificate issued by a trusted CA. I\'m using signtool.exe from the Windows SDK v6.0a.
The certificate is located in the computer
I've had this problem as well. Still not quite sure what caused it since I never had the time to find out. The thing I found was that the private key went missing!?
I did what coder_2007 suggests and it worked for one complete automated build but the next one would give the same error. So something on my build server broke the private key after a complete build (including several signed applications).
What I finally ended up doing was, immediately after importing the PFX, to go to %allusersprofile%\Microsoft\Crypto\RSA\MachineKeys and write protect the latest file (the one that match the time of import).