Have the same problem on my MacBook Pro with Ubuntu 11.10.
The "Ubuntu Welcome Jingle" was played successfully after Ubuntu booted up from LiveCD, but the screen remained blank. A wild guess would be that simply the right display was not configured correctly (by the way it has Sandy Bridge CPU with an external AMD Radeon GPU).
Have the same problem on my MacBook Pro with Ubuntu 11.10.
The "Ubuntu Welcome Jingle" was played successfully after Ubuntu booted up from LiveCD, but the screen remained blank. A wild guess would be that simply the right display was not configured correctly (by the way it has Sandy Bridge CPU with an external AMD Radeon GPU).