The error you posted does not point to any mojoPortal code to diagnose an error happening in mojoPortal I would need to see the error stack trace which shows where in mojoportal code an error is happening, assuming that file system permissions are correct and the user that is the identity on the application pool has full control over the /Data folder and all child folders and files, then any unhandled error should be logged in the mojoPortal log as discussed in Basic Troubleshooting.
In the absence of an error stack trace that points to mojoPortal code I can only guess that something is misconfigured on your server or IIS web site.
Based on the error you posted:
"Forms authentication failed for the request. Reason: The ticket supplied was invalid."
which is happening only when you click on links for pages that live in the /Admin folder such as /AdminPageSettigns.aspx or /AdminManageUsers.aspx
possible causes I can think of are:
- if there was an another web.config file in that folder it could have a different machinekey so the forms auth token from the machinekey in the mojoPortal root folder Web.config is not valid in this folder because of a different machine key. machinekey is used for encrypting the forms auth token and only the same machinekey can read it.
- you have a web farm environment and you don't have the same machinekey on all nodes
- you have configured the /Admin folder as its own application below the mojoportal site in IIS
makes sure the IIS web site is configured for anonymous authentication
make sure also you have all windows updates installed