Okay, I'm sitting at my mom's newspaper office on the iMac that I adopted (for use only when it's usual operator is absent

) And my mom exclaims that her iMac G3 has shut itself down while she was typing in InDesign.
I just blew it off as something she had done by accident (my mom is no computer genius) And didn't think of it again. Then it kept happening. And just about three minutes ago, it happened again and now her date and time is all messed up. At first I decided this was a battery problem. But then I remembered that an iMac's only warning of a dead battery is a black screen at start-up. But another sign is the date and time problem.
If anyone can maybe give me an idea of what's goin on, I'd appreciate it.
She's running a Graphite iMac G3 @ 600mhz
--OS 9.2.2
--256 mb RAM