So...about two weeks ago my girlfriend complained to me that while listening to her (my old) 3G 20gig iPod, she heard a popping noise similar to a static pop an a notice read on the screen that said there was no battery life on it, and it shut off.
She was unable to use the iPod on the rest of that trip, but took it home and charged it. Since then, the amount of charge the battery meter shows has been inconsistent, and often it does not recharge the full amount, even after sitting on the dock charging for hours. Additionally, the same inital problem has happened to her a few times since then.
Today, my 3G 40gig iPod experienced something similar. While listening to my fully-charged iPod, the battery meter went, unexplicably, to zero, and I had an error message on my screen saying the battery life was zero, and it shut itself off. I turned it back on, got the restart Apple logo, and played another album. It played through the album fine, and the entire time the battery meter slowly went all the way back up near 100%.
After that album finished, I went to play another, and the same probelm happened---battery life to zero, and it shut itself off. I tried a few more times to get it up and running again, but to no avail.
It seems weird we would both have the same problem within weeks of each other. Both iPods are less than a year old--hers (my old one) I have the warranty on; the other I bought secondhand and have no warranty on.