I just got this error on my 5th gen 30g Video. A year ago, I replaced the factory battery, headphone jack, and hold button (easy switches). Recently, my ipod has been freezing and shutting off for extended periods of time. Today, it shut off completely and would not turn back on. (Does anyone know if replacement batteries still give the 'sad battery face'?) I took it apart to detach the battery and reattach it and I got the aforementioned error. I took it apart again, detached the battery, detached the hard drive, cleaned out some dust that seemed to enter my lungs, and reattached all and it worked.
If you have any problems with your older ipod, do not hesitate to buy some cheap parts for it overseas! I think the battery was $3, headphone jack/hold button was $0.99, and a faceplate was $5. Sometimes the faceplate will break when you take it apart, so always have a back up! There's not many parts inside, so it's always an easy troubleshootin process..and you feel like the bob vila of ipods afterwards.