If you have an upgraded hdd and updated to 3.41 fw recently then download the fixed version of 3.41 fwfrom sony offical site because this fw has a bug which crippled the upgraded hard disks.
And if u have original hdd which come factory installed then try recovery menu. Since the 2.5 update the PS3 has a Recovery menu. Now how to get access to service mode? follow these steps...
1.Make sure the PS3 is turned off,
2.Press and hold the power button on the PS3 it will power on then power off,
3.When it's off press and hold the power button again until you hear two consecutive beeps,
4.It will ask for the controller to be connected via the USB cable,
5.Turn on the controller, and you will have access to the menu with the following options:
*.Restart System: Restarts the PLAYSTATION 3 System.
*.Restore Default Settings: Reset all system settings back to default.
*.Restore File System: Checks for corrupt/missing system files.
*.Rebuild Database: Rebuilds the OS for the PLAYSTATION 3.
*.Restore PS3 System: Fresh restore; Deletes everything and starts from Scratch.*.System Update: Update the PLAYSTATION 3 System.
Try to use all options one by one and i hope this will help you.