Kantor on 30 November 2011
I had that problem just after I got my PS3 back from repair, about a year and a half ago. The fans would keep running on standby mode (though obviously not when it was off at the back).
I'm not sure why this worked, but it did: I took out the hard disk, wiped it with a tissue, and put it back in. The problem has never reoccurred.
(Former) Lead Moderator and (Eternal) VGC Detective 
