You should be able to post anywhere. Are you sure you clicked the right button? Could you explain in more detail?
Edit: Oh I see your problem
I keep getting the following message when tryin to reply to someones post:
The last posting from your IP was less than 360 seconds ago. Please try again later. The thing you were trying to post was saved as a draft. This limit decreases substantially as your account becomes more established.
I get the message when I haven't replied to or posted a new topic for several hours.
The message was clear, there's someone on your IP that made post less than 360 seconds ago. If it wasn't you then it is someone else. It might be your friends with the same connection as you, or your internet provider is somehow assigning the same IP for a lot of people, and in that "a lot of people" there's someone who made a post in Bitcointalk recently.
I don't really know about IP and connection stuff, but that's it. If you want to remove the time limit for posting, you can wait until your account become higher rank
or you can buy a
Copper Membership now to have the advantage of "Member" rank immediately, that includes less time limit on posting.