Re : can't use prefs as any user, even admin
The problem is with the column registrationDate in the table users_users.
Patch: Can you check if you have this column ? If not add it as defeined in db/tiki.sql
Can you check if you have a value in this column for your user? If not copy the value of lastLogin for instance.
Why: Are you admin? Have you been registered by the admin? Is there something specific to the registration that can help to find the problem.