I can confirm this bug with Ubuntu 11.10 beta 1 on HP dv6-6145eo
CPU: AMD A6 3410MX
GPU: AMD Radeon HD 6755G2 (HD 6520G and HD 6750M hybrid crossfire)
During the boot only black screen is shown (not even the back light is on). I can still hear the login sound so it's only the screen that is not working.
Ubuntu 11.04 works fine.