I reviewed all the permissions and your account settings and nothing jumps out and it seems you've performed the usual trouble-shooting steps on your end. There was also a server issue which caused an outage late on 10/30 and which was resolved on 10/31. It is possible that this was causing issues with your posts - especially if you were trying to add attachments.
Try posting again and, if the posts fail, send me a PM with the time of the failed post and a screen shot and I'll see if I can find something in the error log.