[ubuntu] stuck at loading screen

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http://ubuntuforums.org – I installed Ubuntu on my new Dell laptop and for a few days everything was ok. Once I started my computer I saw "your system is running in low graphics mode" window and then some window with four buttons, which I couldn't choose (it didn't react). I have no idea why it came up, I installed a few programs earlier, but nothing strange, all from Ubuntu Software Center... Anyway, I reinstalled ubuntu-desktop, gdm and fglrx and now when I start Ubuntu it gets stuck at loading screen with five blinking dots. When I press "Ctrl + Alt + F1" I normally get into Terminal and I can (Hardware)