This post is courtesy of Trent F. Thanks for the input.
Depending upon your system settings, you may have trouble saving the Signature.psd file after you edit it in Photoshop. If you're on a windows machine, Trent suggests the following;
... I don't know if anyone else has had this same problem with a locked file but I figured a work around. I talked to my brother who is a computer geek that works for Microsoft. He had me do everything you suggested and realized that you can't lock a file in Wiindows.
I just copied the file [Signature.psd] to the desk top where I could edit and save the new signature block. I then deleted the file out of c/ drive and copied the file from the desk top back into c/ drive and everything is groovy...