Every new member can start a thread.
I see sometimes new members that are looking at an "no permission" error.
This happens when they did not complete the registration procedure.
They still have to click the link given in the mail send to their email address.
The only exception is the flea market, for posting there you should be a senior member with at least 100+ posts.
We have noticed that the forum software sometimes has a hick-up.
If this happens you can not start new threads. (it even happens to me sometimes).
You can try to start a thread with a title shorter as 20 characters.
Most times that works.