i was doing routine work when my mac began to lag, i decided to reboot, unfortunately without success. it just did log in to the mac os so i decided to reinstall. i formated the disk and made the usb mac os 10.8.2 installer. but the installation freezes at 24 sec. i have no idea what to do. one thing strange is that i can install win 7 and use it without any problem. i have macbook pro 13 early 2011 with 8gb