Signing code with a pfx file

I have a pfx file containing both my certificate and my private key.
I have entered it into visual studio together with my password.

Now, when I run Build Solution, it prompts me for the password, when I enter the password, it throws this message at me: "Object already exists".

In the error box, I get this error: Importing key file "codesigning.pfx" was canceled.

I'm wondering what might be wrong, if I generate a selfsigned key it works fine.

I generated the key with openssl to a .p12 file, imported it to windows, and exported it to a pfx file, with both the private and public key.

Any ideas of what is wrong? Do I need a certain extension when I generate the certificate and key?

I used this as my extension for generating my certificate:

[ codesign_ext ]
extendedKeyUsage = codeSigning,msCodeCom

But I still get this error

I've got the same error after upgrading my development environment with VS 2005 SP1. I wonder if there is an incompatibility and I will have to remove the pfx file and create a new one.

SimonJ

I installed SP1 a few weeks ago, and generated the pfx file today, so I don't think that is causing it, but I'm going to test from a machine without SP1 installed.

UPDATE: Just tried it with a machine without SP1, same problem.
I can easily select the certificate and get it loaded, but when I build, it asks for the password again, and this time I get the messagebox and the error.

Any ideas, or any way to get a bit more usefull information that just "Object already exists", since that doesn't really point me to whats causing the problem.