Server Error & core. file loading in ftp
 

Yesterday around 8pm my site went down and displayed Server Error message.I've repaired the db tables, cleared cacheusing tools.php, and still no joy...just checked my ftp and found loads of files named: core.9964 and so on...do you think I've been hacked or something?

I've a core file that's now dated for tomorrow, 11th Aug?