Strange thing on new wordpress

Hi there.
So ive create a new wordpress blog and have finished the work(add new template, edit the template, etc…) and now i was adding some posts, but when i try to add new categories ive recieve this message “You don’t have permission to do that.” wtf ?!
And i cant add users too.
Im using 2.1.2 wordpress version and i never add this type of problem, damn wierd.

Anyone knows what is the problem??

Thanks in advance