A few weeks ago my mid-2007 iMac hard drive was making clicking noises and showed signs of failure, so I took it in to an authorized service provider and got a new hard drive put in. I brought the iMac home and restored from my most recent Time Machine backup without any problems. However, I now get random freezes that cause me to restart my Mac every time in order to clear up the freeze. The freezes seem to come out of nowhere - one time I was just watching a YouTube video when it froze. When it's frozen I can move my cursor on the screen, but nothing else responds. I can hear the hard drive working while it's frozen. I've had four of these freezes so far and I never experienced a problem like this before I got my hard drive replaced. So I'm wondering if the problem might lie in the hard drive that got put in, or if I restored from a bad backup and I might need to restore everything again?