Suddenly, i can't login with my host account.
The error message i get is (the resource key for the error message): LoginFailed.

I debugged the login code, and the reason for the failure is because
both objAuthUser object is null (isNothing) and also the object objUserInfo is null.

I registserd new user and logged in successfully, but when i changed it to be super user
account (in the db, in the table 'users') - login is failing again.
When i change back to be regular user - login success.

How can i register some super user account to control my portal
or fix the host account?
any ideas??

Thanks.

Did you recently upgrade your DNN?  or revert to a different web.config file than the one you installed with?  The original web.config file has some info like this:

    <machineKey
      validationKey="F9D1A2D3E1D3E2F7B3D9F90FF3965ABDAC304902"
      decryptionKey="F9D1A2D3E1D3E2F7B3D9F90FF3965ABDAC304902F8D923AC"
      decryption="3DES"
      validation="SHA1"/>

and if these keys change, your site will still work, but you wont be able to login to "admin" or "host"

Correct me if I am wrong on this.