I forgotten my previous firmware was either 3.55/3.56... I downgraded to 3.41 and in the service mode, system setting shown i have 3.41 firmware... I tried putting lv2diag (file 2) into my usb and the ps3 doesn't exit from service mode.
Try to download the lv2diag (file 2) from a different source and try and use that. If you did indeed attempt to downgrade from 3.56, like the previous poster stated, you are stuck till a solution surfaces. I would advise greater caution in the future to avoid things like this.