My brand-new HP29C (S/N 1711Axxxxx; got it on ebay a few weeks ago) gave me a scare: keys pressed in run mode would have unexpected results. For example, the 7 key pressed several times would put different numbers on the screen.
I removed the battery, and let it recharge for half a day. I put it back and the machine is working fine. I can therefore assume that the problem was low battery, even though the low-battery indicator (it's all the decimal points but the real one lit, right?) was NOT on.
For what it's worth, the battery pack has been rebuilt using Radio Shack 1000mAH NiCd cells (it arrived this way).
Comments?
/ji