I am upgrading an install of DNN 7.0.0.4 to DNN 8.0.0.4.  I have a full backup.  I have uploaded the upgrade using FTP.  I cannot get the upgrade script to work at this point.  I have set autoupgrade to true in web.config.  I have manually entered the URL for the upgrade, but nothing occurs but a blank screen.  What am I missing?

I have successfully upgraded two other portals from 6.2 to 8.03 by simply FTPing the unzipped upgrade over the previous installation (after all necessary backups) and then going to

http://MYWEBSITE/install/install.aspx?mode=upgrade.  In essence, I simply followed the instructions here http://www.dnnsoftware.com/wiki/upgrading-dotnetnuke. After uploading the upgrade, I would access the above link on the portal, log in as host, and the site would launch the Database upgrade.

The previous installs went flawlessly with no issues.  I then attempted to upgrade a 7.03 portal to 8.03 using the same process, but this time nothing happens. When I go to ../install/install.aspx?mode=upgrade there is only a white screen.  When I change the web.config autoupgrade flag to true, nothing happens.  It is as if the site does not even recognize that I have uploaded the upgrade.