Everytime I try to post something it says I have posted to recently (360) seconds. Yet I haven't posted anything in months.
If you have recently signed in within the lats 6 minutes then you will not be able to post as a newbie.
If someone else that shares your IP address has logged in or posted in the last 6 minutes then you will also not be able to post. This is true even if the person who has posted has a higher bitcointalk rank then you.