That's actually a problems that affects a number of games. Some think it has to do with OS X not recognizing that a game is in progress, and trying to put the system to sleep.
Here's what to do...
1. In Energy Saver Preferences, make sure your computer is set to never go to sleep.
2. Make sure that it is not set to put the display to sleep.
3. Make sure it is set not to put the hard disk to sleep when possible.
I use to have the same kind of problems when playing Starcraft. As soon as I made those changes, it never happens anymore. Once you're done playing, just reset them the way you want them.
Also, if it happens again, just close the lid on the iBook. Wait a few seconds and then open it. After its open, it will take a few more seconds for it to go to sleep, then open the lid to wake it up. A lot better and easier than pulling the battery.