Parental Controls locks up computer and crashes

I have had similar issues with parental controls. Are you current on your Leopard system updates? There were a lot of fixes related to parental controls. I have not had nearly as many crashes since 10.5.4. Notice I did not say zero crashes. I had kernel panics on my daughter's machine dealing with parental controls. The final solution was an archive and install. Since the archive and install, no panics on her machine. Any crashes I have had are system preferences needing force quit while viewing details of one of the kids' accounts over the network from my machine. Call Apple. You are within your free support period. They should help you. They have been very helpful when I have called them. Call AppleCare and have your serial number handy. You don't need to buy AppleCare unless they refuse to help you because your system is too old. If it's not a year old yet, I suggest you consider AppleCare. It's not really any more expensive than Dell CompleteCare and I like dealing with Apple a whole lot more than I ever liked dealing with Dell, HP or Microsoft.