I tried 12.10 and 12.04, 2 live USB creators and the tutorial how to create an bootable usb drive under OSX. I burned DVDs with the mini.iso 64bit.iso and 64bit+mac.iso, nothing is working.
The farthest i got is beyond the first purple screen which switches either to a red square with a yellow line or some long text error messages and stops loading.
Do i really have to try an older version and update to 12.10? Or is there a way to install ubuntu on an external drive (e.g. the macbook hdd)?