Something has definitely gone wrong with Ubuntu and Macs. A 2011 MacBook Pro in my case. I have just spent a frustrating two days trying to boot from the CDs that I downloaded. I've followed all the instructions and I have partial success but it always fails with the message 'Unable to find medium containing live file system.' I've also tried making bootable flash drives as per instructions but my Mac won't even look at the results.

I've successfully installed earlier versions of Ubuntu without any problems on Macs a few years ago but this latest version has me stumped. Judging from this thread it seems that I am not the only one having this problem. Maybe it's time that the wise men tried to fix it.