MyBB Community Forums

here is the page of the problem : http://gco-forums.com/showthread.php?tid=5
as you can see the content of the thread is unreadable ( the real text was : This is a testing thread by DzGangster).
image : http://postimg.org/image/ngkhdis7j/

please help me !

i tryed to desactivate all plugins but it didnt work
i also changed the theme
i also changed the browser, deleted cookies...