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I have a Lenovo Thinkpad T400, connected to an IBM omniport dock. To this is connected my IBM ThinkVision monitor, via DVI cable. My Thinkpad is running Ubuntu 11.10. The monitor is not being detected, though it is on.

I'm a huge Linux noob, so please don't be too harsh. How do I fix this, or at least start diagnosing the problem?

EDIT: My video card is ATI Mobility Radeon HD 3400 Series. I have the proprietary driver disabled. When I go to "Additional Drivers", I see "ATI/AMD proprietary FGLRX graphics driver" and "ATI/AMD proprietary FGLRX graphics driver (post-release updates)", both disabled. When I enable the first one, nothing changes. When I try to enable the second one with the first one enabled, I get update failed.

EDIT 2: When I have the first driver enabled, and run sudo amdccle, I also get an error. This command does not work with the driver disabled.

EDIT 3: I forgot to mention this, but when I boot with Windows on the same machine, the monitor works just fine (via DVI).

I think the problem was caused by the fact that I have 2 graphics cards - one integrated Intel card and one ATI card. I connected the external monitor via DVI port, which was likely associated to the ATI card, which still has some issues (I don't know why, but would love to find out). I changed connectors and used VGA, which resolved the issue.

However, I would really like to get my ATI Radeon Card working, since VGA is really grainy compared to the DVI I get on Windows.

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