I'm not getting very far with the software developers so I'm now appealing to the experts here to find a solution to my problem.

It appears mod_security is triggering on the word nmap within a forum post, preventing replies to the thread. Link is here: http://www.globalaffairs.org/forum/threads/nmap-6-released.68912/

The mod_security log shows the following:

Access denied with code 501 (phase 2). Pattern match "(?:\\b(?:(?:n(?:et(?:\\b\\W+?\\blocalgroup|\\.exe)|(?:map|c)\\.exe)|t(?:racer(?:oute|t)|elnet\\.exe|clsh8?|ftp)|(?:w(?:guest|sh)|rcmd|ftp)\\.exe|echo\\b\\W*?\\by+)\\b|c(?:md(?:(?:32)?\\.exe\\b|\\b\\W*?\\/c)|d(?:\\b\\W*?[\\\\/]|\\W*?\\.\\.)|hmod.{0,40}? ..." at REQUEST_HEADERS:X-Ajax-Referer. [file "/usr/local/apache/conf/modsec2.user.conf"] [line "149"] [id "959006"] [msg "System Command Injection"] [data "/nmap-"] [severity "CRITICAL"] [tag "WEB_ATTACK/COMMAND_INJECTION"]

This is the first time I've run across this, but it seems to be a common occurrence with the Xen Foro software package. If a post contains a key word as defined in the mod_security rules, replying to the thread is prevented.

Personally, I feel this is a software issue with Xen Foro. But I'm covering all my bases in my search for a fix.