Today I had Leopard crashed on me. I was working on setting up home network and noticed that whatever I lock I could not unlock, the button would not respond. Then I decided to restart and it would not start up. I had gray screen with apple logo and spinning wheel. Tried disk utility and whatever apple recommends. Called Apple - waited for 55 minutes. While waiting decided to use Time Machine system restore option - worked. What happened - I don't know. When I was using Tiger I never had this happen to me. May be it was a glitch or I did something wrong 
