Originally posted by KHATPHAT
Is your ps3 jailbroken or not?
Maybe is overheating since almost all fat ps3 suffer from that issue.i could also sugest opening your ps3 and cleaning it and using a air Duster to clean dust and stuff inside.and also apply new silver artic themal paste to cpu and gpu.You can also try and reinstall the firmware again.
im on rogero 4.55 cex cfw and i have changed up firmwares to rebug 4.46.1 rex or whatever it was called and it still shuts off.. so i think its because its outdated, old, and overheating ;[