Why won't my iPod charge?

First suggestion: try a hard reset... (Press and hold middle button and play for 10 seconds) If that doesn't help, it may be a hardware problem. If the iPod is within warranty (1 year, I think), Apple will fix it. Otherwise, it's only really worth 10% off a new one (also from Apple).

If you are in the diagnostic mode the best bet would be to hold down the MENU and center button for six to ten seconds.

Also, what model iPod do you have? Is this a new charger? Do you have the ability to connect the iPod to another computer to see if it is your cable or charger?

Same thing happened to my iPod, but I still can use it when hooked up to power. Like Ben said, hardware problem.

There are three hidden iPod commands (Hard Reset, Diagnostic Mode, and Disk Mode) -- they vary depending on your iPod model. You probably need to do what themacallan suggests, but you can see the commands for other iPod models here: http://www.command-tab.com/2006/03/30/hidden-ipod-commands/

Thanks guys - Hard reset did the trick. I didn't know it existed.