I just replaced the battery in my iPC and had a real head scratcher going.
My iPC has the ASUS A7N8X-VM/400 mother board in it. It takes a 3volt CR2 lithium battery. The one that looks like a stubby AA battery. Anyway, I took out the old battery and replaced it. Started up and reset all the BIOS info. The board started up no problem. Job done, I thought. I have my board plugged into a plug strip which I turn off at night. Came in the next day and upon turning on the plug strip and restarting all of the BIOS settings had been lost. After much fooling around, checking the voltage of the new battery, cleaning contacts etc with no change I noticed that the battery has a heat shrink label on it that extends down and covers a bit of the bottom of the negative end of the battery, enough that it got in-between the battery and the contact on the board. Took a razor blade, removed the heat shrink and now all's good.
Anyway a long winded way of saying check out the bottom of the battery before you install it.