Unauthorized Tcode Access

Dear gurus,

I have problem like this:

On November 2010, I see from ST03N that a user has access to tcode FBZ1.

From roles assigned, that user has no access to that tcode (I saw in menu and auth object S_TCODE).

I tried to login as that user, and I can't directly access by typing FBZ1 from the tcode shortcut.

From SUIM -> change document, I see there's no additional role assigned or role change to that user.

What could possibly allow that user to access that tcode?

Thanks for help.

Best Regards,