Hi kingspen,
I just tried to send a private message myself and was able to do so using FireFox. Try logging out of the site, closing all browser windows and clearing your browser
& flash caches. Log back in and try to send the message again.
If that doesn't help you can try switching to a different browser for just a moment to see if you can send the message. If you can send the message in a different browser it might indicate a problem with your primary browser.
If neither of these suggestions solves the problem then please let me know.