when I start the computer, makes a big high pitch sound and the only thing I can see on the screen is "[[23" written everywhere . I have to start it always through the recovery mode. Ubuntu desktop screen does not flick, but every window that can maximmize and minimize does it like crazy. Like firefox browser, terminal, vlc.. I have a Lap top Acer Aspire One with AMD/ATI graphic card. I read many forums about flickering screen and I try many things , but I still have the problem. I am very new in Ubuntu. Please help