I finally was approved.
I posted in the General Discussions » New Feature Requests.
Topic is: testing a post using firefox browser.
No problems.
What you may try is turn off. Or I should say turn on
Disable HTTP Referer Check?
Under Control Panel » Primary Settings/Advanced Options
Then have the member try to post.
If successful that will at least tell you he has a security setting somewhere that blocks him.
It could be a firewall setting or internet security setting.
For me I have HTTP Referer Check disabled because most of my members do not have control over security settings.
Anyway you can have your member post a reply to test or delete my post and registration.