Mac OS X Quits Unexpectedly & Must Restart Window??

Okay so I could be doing anything on my Mac, running a few programs or a lot. And it would just crash, turn off, shut down, however you would put it. When I turn it back on and log in, a window pops up saying my mac restarted cause Mac OS X quit unexpectedly. Now that's been happening at least two or three times every other day... What could be causing this, it's also setting my date and time back to 1969...??
Now other times, or even sometimes right after I log in and correct the time a greyish window will pop up saying that I have to restart my computer by pressing or holding the power button?? which pretty much freezes my computer so I have no choice but to do what it says. What is that??

This has all been happening for a few weeks I think. Please help me!

I can't be absolutely sure, but it sounds like your PRAM battery may be close to running out of juice. You might try replacing it to see if that resolves the rebooting and the date getting set back to 1969.

You can get instructions on how to change it out and also buy it from the folks at iFixit: The free repair manual.

Thanks so much! And I've looked into that, would it be safe to install it myself? I'm not to keen on opening up my PowerBook myself. Also, how would I know if the PRAM battery is compatible with my PowerBook?

Just go to iFixit: The free repair manual. They have step by step instructions on how to change out the battery and also sell the correct one for your PB. And yes, you can do it yourself if you're careful and can follow instructions.

Thanks a lot, I'll see how it goes then.