I did all security stuff there , but again my site hacked by : aSSaSSin_HaCkErS

I just installed a pure vbulletin , without any adds on or syle .

and I did all security stuff .

but again this happen .

--------------- Added [DATE]1226398803[/DATE] at [TIME]1226398803[/TIME] ---------------

vbulletin stuff just want to say its not a vbulletin bug , but it is .
I even installed vbulletin 3.8 beta 2 . and same thing happend again .

3.8 beta 2 is just that a beta. It is not a stable, and supported, release.

I'm not saying that this is why you're getting hacked but don't assume that 3.8 is stable just yet.

Try hiding your vBulletin version and adding .htaccess password to your admincp directory.

Ya, and can we assume you've changed all your passwords? Not just you, but all other admins & mods. And any FTP and Cpanel account passwords also. And be sure to file tickets with your host, as it could be someone hacked into the server.