Did you just upload the VB files to your root directory and then run the upgrade.php?
If you did the first and NOT the second then you need to run the upgrade.php (found in the install directory) DO NOT run install.php
If you did both of them you need to do the 2nd part of the error report:- The datastore cache may have been corrupted. Run Rebuild Bitfields from tools.php, which you can upload from the do_not_upload folder of the vBulletin package.
In the zip file you downloaded should be a directory: DO_Not_Upload.
In that directory will be the file tool.php, copy this to the root directory of your site and then run that.
Then select:- Rebuild Bitfields. This should solve the problem/s