Why the hell can't I write PMs or use the search?

When I write a PM I get the error "The last posting from your IP was less than 360 seconds ago. Please try again later."
Of course, the error is BS, as I didn't send any PMs at all.

I'm really frustrated as I need to reach a Bitcoin Forum member urgently, how can I fix this?

By the way this is really user-unfriendly, if I'm blocked from sending PMs then please at least tell me so BEFORE I type my message...!!!