It appears you nailed it, IBJoel - the post by OP here has a number sign in it that the system is turning into a link.

This is perhaps an unforeseen (and IMO unfortunate) circumstance/glitch of automatically linking hashtags - new members can't put a number sign in their post, which is of course not a link until the system creates one on it.

To fix this, I might propose one of the following:

• Turn off automatically linking hashtags (proposed previously and turned down)
• Allow hashtag links by new members
• Change the "this post is not allowed because it has a link" (or whatever it says) page to indicate that they need to remove any number signs from their post or they won't be able to post it.