I had a 24" core 2 duo running PT 7.4.2 on SL. I often had problems with different things freezing up (ranging from itunes to system preferences) even when I was not running PT. Just this past week I picked up a new 27" i5 and have been running it with and without PT 7.4.2 installed. I have noticed with PT I have frequent hangups, without I do not. Has anyone else noticed any issue like this?