There is a
thread running in Feedback on this very subject. That error message usually means your IP address has been blocked, because it (or the enclosing range) were used by multiple spammers. At least, that's the case in the forums - the front page is run by different people.
See the Feedback thread for further details - it is possible to refine blocks to exclude smaller legit ranges.
Note that the Team MacNN forum covers 'distributed computing' - our efforts to take over the world. This is somewhat different from website support, which is what I think you're looking for.