Did you use the new Web.config that ships with mojoPortal or try to keep your old one? You should use the one that ships with mojoPortal and restore any customizations such as machine key from your old web.config to the new one.
You may also need to check file system permissions, if it doesn't the user that is the identity onn the app pool doesn't have read permission on the editor files it will cause errors. You can use the network tab in Firebug to see if any files are failing to load.
Hope that helps,