Linux NooB to World: Can you help me out?

I use Ubuntu. I’m running 12.04 Precise. My laptop has a 64-bit i5 processor with an AMD Radeon 6550 graphics card. Trying to troubleshoot a failed installation of the proprietary driver for the graphics card is another name for the fifth circle of hell. I am not kidding.

[Edit: a correction, courtesy Sayash: X is the drawing system. It uses display drivers to interact with the graphics devices. The standard display driver is called “radeon” or “ati”. I wasn’t joking about being a Linux newbie.]

So as I understand it, the X system is the simplest video driver for Linux. It uses system memory (RAM). Then there are the fglrx drivers, an open-source set of display drivers that run the graphics card. There are also proprietary drivers for the graphics card written for Linux supplied by AMD. This driver–or set of drivers–is called Catalyst.

For a long time, I had just the fglrx drivers installed. I didn’t face much trouble, but then I don’t do much with the laptop that uses the graphics card strenuously–g++ runs just fine on standard memory. I installed the proprietary driver, with some trial and error and lots of help from people, after somebody told me about them. The proprietary driver is better-performing than fglrx. Transitions became smoother, for example.

However, the proprietary driver has a habit of conking out; it has done this twice before. Ubuntu would go back to the X system, I guess. Both times, all I had to do was to reinstall–I say “reinstall”; I mean type ./installer from a shell and press enter–the driver and all would be well again.

This time, though, I was locked out of the GUI entirely. And no amount of fiddling, wheedling, or ubuntuforums drudgery brought back the GUI. I tried installing fglrx instead of the proprietary driver. I still get only a shell when I first switch the computer on. I have to log in and say startx, which brings me to the Desktop without the Dock or the system tray. I then have to start or restart lightdm — the desktop manager to get to the Ubuntu login screen, after which everything proceeds as usual.

Unless the shell loses its connection with the X server, which happened twice… afterI had installed fglrx.

Needless to say, I am bugged. Has anybody seen this sort of thing before? Do you know what the problem is and how to fix it? Please please help.