I have just removed the proprietary fglrx driver on ubuntu 12.04 on my hp pavilion dv6 using the system settings > hardware > additional drivers method. When I reboot, ever second boot succeeds with the other going into a black screen, although I can hear that ubuntu has started and requesting a login in the background. Usual drum sound in the background.... I have searched on various forums but none describe my specific issue. I have tried several times and it is only every second boot.

Any advice will be greatly appreciated...