Here is a wild guess. In Cpanel do you have hotlinking enabled.
Maybe the settings are incorrect.
Or again open a support ticket.
Thanks for taking a peek Ruben. I turned off hot linking protection - I had it on and it was causing an issue somewhere - I forget the details but it wasn't with my forums. But it is off at the moment. I guess I will need support for this one - it has been malfunctioning for too long... I too think it is likely a server issue but what is causing this behavior is beyond my knowledge and ability to determine.