I've installed Ubuntu 16.04 32bit on a Macbook 2.1 of 2006. After the fresh install at first reboot/startup the macbook freezes at purple screen. The interesting fact is that, after the freeze, if i force shutdown with button, it reboots and goes to grub page where i can boot finely from. If i try to get grub on sturtup and then start ubuntu from grub it freezes again on purple screen. So, i can boot finely only after i force shut down with button. i've also tried Linux Mint but with same results. I've tried a cuople of solution found online but nothing worked. In gparted, grub partition is 1mb and signed with a red sign. is that the problem?