Hi Tim,
Yes one of the members reported this this morning and i restored the yesterday night's backup. Fortunately, we are getting daily backups.
It is the attack from a group (probably lots of lamers guided by a few hackers) from Turkey (at least they say so). Fortunately, their aim is not to kill whole site. They replace the index page of the site or do a similar thing.
In their little mind, they are doing something useful for Turkey and turkish people by trying to give messages to lots of people but the strange thing is that this time the site owner is turkish too.

) As far as i understand they search on google for popular sites with popular softwares installed (like vbulletin) and use their bugs to replace their index pages.
Anyway, because of daily load on me, i could not upgrade the vbulletin

. I will try to be more serious about this later on.