lol your going to think im stupid but i fixed my ipod today after it broke 2 years ago. Simple way to fix it, no it doesn't include opening it up or rebooting the whole thing its really simple.

step 1: Get something to help obsorb shock like a paper book.

step 2: decorate it.

Step 3: Hold your ipod firewire port down and gentley wack it against the paper book.

Trust me it works and if you want to know why its because your ipods hard drive has most likely come loose by doing these steps it puts it back to place. Ive tried it on 2 ipods and its worked both times :) if that doesn't fix your problem your files could be corrupt which just involves rebooting it "holding menu and select for 6 seconds" i personally like the smashing it idea because its the only thing thats worked for me belive it or not lol.

Either way if your ipod has the sad icon try this out it worked for me!