OK...so I'm not quite sure what happened, but this time it worked. I could have sworn that I deleted the vendor.xml file, but when I just went back to check and make certain...it was still there! I deleted it.
The other change I made in my previous attempts was I replaced the Blackberry.alx file with one that was provided by another user on this forum. I decided to revert back to the original one.
That being said, I'm not certain if it was the ALX file, the XML file, or both. Either way, it seems to be working as I am running the upgrade process while writing this post.
Thanks for your quick response!!!