I recently installed Ubuntu 12.10 64 bit version on my Toshiba Satellite with AMD Radeon dual grahpics alongside windows 8 and whenever it boots up it first stops at the purple screen for about 20 seconds then starts to madly flicker between bits of writing and the Ubuntu boot logo and after a long time it finally stops and then Ubuntu boots up. I don't know what is happening but i gave the same disk that i used to my friend and his one works fine. My video graphics are fully updated as well.
I hope you graphics card is not identified by the Os.So I hope if you disable graphics card you can stop that flickering effect. To disable graphics forms are available in ask Ubuntu.Please search for blacklisting graphics card.The window of Ubuntu sometimes will not be so smooth.Reconfiguring graphics can also be a possible solution.