After my iPod (3G 15GB) spent a couple of weeks sitting stoically alone in my backpack, I pulled it out only to find that the Apple symbol was displayed indefinitely. I'll call this the "Continuous Apple Symbol of Musical Death" (CASMD).
After various iPod updates on Mac and PCs, disk mode mounting, and complete erasing and reformatting of the drive, I was still receiving the CASMD. So I pulled up macosxhints.com and macgeeker.com to find a solution. Well, a solution I did not find, so I started troubleshooting by putting the iPod in disk mode (reset with Menu+Play buttons, then hold Forward and Backward before the CASMD appears).
From the Terminal, pdisk /dev/diskX -dump (where X is the iPod's disk number) revealed that I had an intact partition table that looks like this:
Partition map (with 512 byte blocks) on '/dev/disk2'
#: type name length base ( size )
1: Apple_partition_map partition map 62 @ 1
2: Apple_MDFW firmware 65536 @ 63 ( 32.0M)
3: Apple_HFS disk 29231920 @ 65599 ( 13.9G)
Device block size=512, Number of Blocks=29297520 (14.0G)
DeviceType=0x0, DeviceId=0x0
This indicates that the MBR (#1 named Apple_partition_map) was functioning, I think. Since I had run Disk Utility and verified the disk partition, I concluded that this was also functional. That means #2 firmware is the culprit. I used dd if=/dev/disk2s2 of=iPod_firmware.backup to make a copy of the firmware for restoration purposes. I don't know if this is needed, espcially since I was theorizing that it was corrupt, but everything else I read recommended this backup. Then I used pdisk to edit the partition map. It now looks like this:
Partition map (with 512 byte blocks) on '/dev/disk2'
#: type name length base ( size )
1: Apple_partition_map partition map 62 @ 1
2: Apple_Free Extra 65537 @ 63 ( 32.0M)
3: Apple_MDFW firmware 65536 @ 65600 ( 32.0M)
4: Apple_HFS disk 29166321 @ 131199 ( 13.9G)
5: Apple_Free Extra 63 @ 131136
I simply skipped the orginal firmware sectors and place a partition of identical size, name, and type, in the next sectors. I subtracted out the remaining sectors (29166231) and created the disk partition. pdisk returned an error if I tried to use the last 63 sectors, but I don't know why.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2006021923332755