If you get a message that you can't post so soon after a previous post, it's likely the automatic spell check feature. You need to go into your profile and turn off automatic spellcheck.
To turn off the automatic spell check, go into your profile ("My Profile" button above this post) and you'll see a section that allows you to turn it off.
You can still use spell check by hitting the Spell Check button under your post, it just won't do it automatically. Since this is a free spell check feature and a lot of people really like spell check, I don't want to remove the mod because of this minor problem.