How does TAC work together with the user permissions module?

Hi, i'm quite new to Drupal, so maybe im missing the point here.

I've installed TAC on a Drupal 6 installation. I've when set up permissions for my forum with TAC, but i can't get them to work properly.
Basicly i've have granted only viewing access to authenticated users, no posting og editing allowed. Then i've set up a moderator role, witch a capable of viewing, creating and editing posts. In user permissions i've granted no permissions to authenticated users and moderators, assuming TAC will ovrewrite the actions and grand permissions. With testing the forum with both authenticated users and moderators, no one are allowed to post.

When i tried to enable the "create forum topic" in user permissions. Testing again, now both authenticated users and moderators have access to posting.

So the $1000 question. What does user permissions control and what does TAC control?? I haven't been able to figure this out.

I tried the same scenario with the forum access module, but i get the same result.

YES, i have only enabled on module at the time (meaning forum access was disabled when test TAC and the other way around).
YES, i have tried to rebuilt node permissions from the post settings menu.

So what to do? Please help!!