We upgraded one of the other portals on our server today. I followed all the rules, make backups of all the files and the database. I even made a spiffy replacement page that said something like "HEY WE ARE OFF LINE FOR A LITTLE WHILE DOING UPGRADES" and all appeared to go well..... until I checked one of the OTHER dnn sites on our server. I kept getting a redirect loop error that was annoying. I finally figured it out. Contact me if you are having that same issue.