TechTV | Secrets of the iPod is a decent summary of advanced troubleshooting techniques, here are the key points with my emphases and corrections/comments]
Resetting the iPodOlder iPods could also be placed in a diagnostic mode(methodshop):
If your iPod's locked up, you can perform the equivalent of a hard boot by holding down the Menu and Play buttons for about seven seconds. This forces the iPod to restart, and hopefully allows it to function as it should.
[jf: This is incorrect. This is a partial reset, which does not resolve the 'unresponsive center button' problem which sometimes afflicts my 3rd generation (3G, smooth wheel, docking port) iPod. A proper reset requires the iPod be attached to a power supply, then switch the hold button to "on" (hold), then switch to "off" (red does not show on hold area) then hold Menu & Play. A full reset will solve my unresponsive center button; a state where part of the iPod behaves as though the device were locked.]
Is your iPod missing in action when you plug it in to your Mac or PC? You can attempt to force your iPod's attention on your computer by invoking Disk Mode on your iPod. To do so, plug your iPod into your computer's FireWire or USB 2.0 port, use the reset button combination described above and, when you see the Apple logo, press and hold the Previous and Next buttons. In short order, your iPod should display the Do Not Disconnect message and mount on your PC or Mac.
[jf: My 3G iPod will mount by FireWire, but not USB. I might try this.]
Restoring your iPod
If you have to routinely reset your iPod or force it into Disk Mode, you should give serious thought to restoring it (iPod-speak for reformatting). Doing so erases everything on the device -- music files, calendars, contacts, notes, and any other data you've copied to it -- so be sure you have a backup of the material.
To restore your iPod, simply connect it to your computer and run the appropriate iPod Software Updater application. Be very careful that you update your iPod with the appropriate version of the Updater. A third-generation iPod can't be updated with the Updater intended for earlier iPods, but a Windows iPod can be (and a 3G Windows iPod won't work correctly with the newer software). Use only iPod Software 1.3 Updater and earlier for first- and second-generation iPods, and iPod Software 2.0 Updater and later for the current third-generation iPods.
[jf: As of 10/12/05 Apple's updater is supposed to work for all devices. The last OS revision for the 3G iPod was 2.3. Just prior to this release the universal updater didn't work on 3G iPods, but this version dhttp://www.blogger.com/img/gl.link.gifid for me.]
Scan the disk
The iPod has the ability to scan its hard drive for errors and repair some of those errors. If you suspect your iPod's drive is slightly funked up, try scanning the disk.
To do so, reset the iPod, and when you see the Apple logo, press and hold the Previous, Next, Select, and Menu buttons. An animated icon of a disc will appear along with a progress bar. This test can take 15 to 20 minutes, so be patient. If your iPod doesn't have a good charge, plug it in to a power source before scanning the disk.
1. You need to restart your iPod before putting it into Diagnostic Mode. Check that your hold switch is off by sliding the switch away from the headphone jack. Toggle it on and off to be safe.
2. Press and hold the following combination of buttons buttons simultaneously for approximately 10 seconds to reset the iPod.
* iPod 1G to 3G: "Menu" and "Play/Pause"
* iPod 4G+ and Mini: "Menu" and "Select"
3. The Apple logo will appear and you should feel the hard drive spinning up. Press and hold the following sequence of buttons:
o iPod 1G to 3G: "REW", "FFW" and "Select"
o iPod 4G+ and Mini: "Back" and "Select"
You will hear an audible chirp sound (3G models and higher) and the Apple logo should appear backwards. You are now in Diagnostic Mode.
4. Navigate the list of tests using "REW" and "FFW". The scroll wheel will not function while in diagnostic mode... (see link for rest of directions)