The best thing you can do is to format your HDD completely.... then once the format done.. prepare a 3.55 OFW on your Flash Disk or some storage device that you can use. Then PS3 will ask (but might not if your PS3 is using a 256MB NAND memory) to reinstall FW... just plug the flash disc with 3.55OFW with it and wait till it finish.
Once done.. search here in forums how to install kmeaw CFW... then reinstall your favorite backup manager. Then do a backup again and see if problem persist again.
Model: CECHC04 PAL/EUR 60GB SKU Console
Firmware: REBUG 3.55 CFW [DEBUG MODE, DEBUG XMB, MENU OPTION 2]
BM: Iris Manager v1.2 (Hermes Syscall8)