"Error 403: Forbidden" when trying to post

[Joel]

I was trying to reply to topics made on my forum but when I do, I get this

Error 403: Forbidden

Return when I type my reply and click "submit" in the quick reply box. BUT ... after I click back on my browser, I F5 the page, and try to click "submit" again, it works, The 403 error doesn't show.

It happens for ALL topics I'm trying to reply to. After I refresh, I can reply to the topic. But on first try, they give me that 403 error. I am an administrator and the owner of the forum. I got full rights and permission to reply to all topics on the board.

My board link : http://www.advertisehotspot.info/

Any idea why?
Your help is greatly appreciated! :great:

 

[Joel]

Anyone knows why this is happening? Apparently only for me, the rest of my members at my forum isn't experiencing this problem.