File Share Encryption

I am trying to add a public key user to a virtual disk and for some reason, the user is not being added.  I am in PGP Desktop, and I click add public key user to the virtual disk drive user access field.  I double click the user I want to add, and their key is moed to the right column under "keys to add".  I click OK and PGP prompts me to enter my passphrase.  I enter the passphrase and the user is still not added to the user access field for the virtual disk.  Am I missing a step?  I have trusted the public key and it is verified.  Is there anything else I must do to add the user? 

Well, it looks like I may have solved another one on my own.  It took me about 4 hours to figure it out, but I got it.  Now, I don't understand why this works now, so I would still liketo know morw about this.  Basically, my passphrase was not saved in my keychain.  As soon as I saved my passphrase in my keychain, I was able to add users to the virtual disk.  Why is that?