UBB.threads PHP Forum Software Community Forums UBB.threads 7 Bug Reports Non Bugs [NOTABUG] 404 Error on Preview

One of my members gets a 404 Error when trying to preview a post:

"Forbidden
You don't have permission to access /XXXXX/ubbthreads.php on this server."

Now I don't have this person's IP in my .htaccess (which is uaually why one would get this error). Rick, any idea what might cause this when he tries to preview?

Basil