buttons are disapeared when changing user rank

[pselten]

I've just taken over a forum for bordercollie lovers. We migraited te complete site to www.bordercollieforum.nl (dutch forum)
The old version was 4.0.6. My version is 4.1.0 sp2. The migration went succesfull, no errors.

But now i've discovering some weird problems.

- when i changed a registred user to the rank of moderator, some buttons disappear for that group.
Now i have quick buttons "arcade" "help" "gallery". These work fine for admin and registred users. All the other groups only have the "gallery" button, the rest is gone.
Also there is no mod link in the above right position for moderators. But the user is able to moderate the postings.

- when i login as admin, in the above right position, i have a link admin and mod. The admin workes fine, the mod doesn't.
I log in, the system said "welkom ..... you are logged in" and redirected me to the same login page, where i have to fill in my user and pass.

- some members are having troubles by login in. They also get the message " welkom ..... your logged in" and after that they returned to the login page over and over again.
note: this specially happened when they are trying to log in without www in the url.

Does someone has similiar problems or know an answer to the above?

Thanks in advance,

Paul Selten.