Looks like he has the proper permissions... should be able to create a thread no problem.
Now I'm going to feel silly saying this but...
It's Lazy Ass Justice.
I'd need to know who the member is. Creating threads isn't restricted for registered users, though the ability can be taken away. Possible his/her account wasn't completely activated.
How long does it take before a new member is allowed to create their own threads? I ask this because one such new member wants to enter the monthly writing competition but currently can't due to said problem.