I can not upgrade to Ubuntu 12.04. I have tried many times with two different commercial DVD's and on two different computers. Both had 11.10 as the OS. Finally got the newer computer to upgrade via download, but older computer will not upgrade at all.
In addition the upgrade attempt on the older computer leaves no OS at all installed. Luckily I have a CD of Ubuntu 11.04 I can reload then upgrade back to 11.10. But I want to use 12.04 on both machines.
Edit: This is on an HP desktop as is the other computer attempting to install from DVD gives a fatal error message which is different each time one was something about a blacklisted file and not being able to calculate the upgrade.