Did you try and download the update from official sony website? or did you get your update from somewhere else? If i were you i would try and go into recovery mode and install the 4.31 ofw update from there and overwrite the bad pup file with the official one. If you dont know how to get into recovery mode you can do so by following these instructions:
Step 1: Turn off your Playstation 3.
Step 2: Hold the Power button down. The system will turn on and turn off once again.
Step 3: Once the system has been shutdown, Re-press and hold you finger until you hear 2 consecutive beeps.
Step 4: When you hear the 2 beeps take finger off power button. You will be promted to plug in your controller via usb and then press the PS button. The Recovery Menu will pop up.
Step 5: Should choose System Update from there and try installing the OFW from there via usb (make sure you have it in the right folder structure on your thumbdrive Folder structure should be "PS3/UPDATE" no quotes)
Hope this helps