I have a prev gen macbook (non unibody), that came with Leopard 10.5. I bought the Snow Leopard 10.6 ugprade, and i installed it. All was fine. No problems. Restarted many times. Today i had to burn a copy of Ubuntu 9.10. I burned it, and restarted the macbook to test the burn. I turned on with the C key, and ubuntu started. It asked for language, and then if if i wanted to try or install. I choose try, and it go on to start, but the macbook would hang. So i turned off, and then on, expecting to see OSX 10.6 again. The macbook started loading, and then the NO/Forbidden sign. I tried to boot using again C key with the snow leopard 10.6 upgrade DVD, but the Macbook would try to boot from the DVD, and then same problem as above (forbidden sign). I then tried to boot with the Leopard 10.5 install DVD, but again, and again forbidden sign. I tried the apple-option-p-r to reset the mac, and then i tried to boot again with Leopard install dvd, and same problem. I tried booting with D key, but nothing happens (meaning it tries to boot from the HD, instead from the DVD). I tried to boot again with ubuntu, and it starts and then hungs. I booted on verbose mode, and more or less this is all i see (edited): ... Waiting on dict id=0 ioproviderclass string id=1 ioresourcematch string id =2 boot-uuid-media ... the iousbfamilly is having trouble enumerating a usb device that has been plugged in it will keep retrying port 4 of hub @ location 0x24000000 ... still waiting for toot device ... the iousbfanumly was not able to numerate the device Any ideas? I have no accessories connected to my macbook. Nothing on the USB.