I have a MacBook Pro one year old with all the updates. Sometimes (about 1 in 25 start-ups) all I get when starting up is an empty grey screen with a sound as though something is stalling, and it won't start up unless I reboot. The sound is hard to explain, it's not beeping, but like it's trying to start but something is preventing it. It always starts up on reboot. Is this something to worry about? I just got the computer back from Apple warranty service with a new logic board and memory, but the start-up issue is still there....is this a hardware or software issue? i have less than a week on my warranty....do I return it again? Or can this be solved in some other way. returning the computer is a 70 mile one-way trip, and I don't want to go back if this is not a hardware issue. I'm still pretty ignorant of Apple system, still trying to learn...anybody help? Thanks