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I have a Macbook Pro 15" i5, and I'm connecting it to a Samsung 40" 1080p monitor.

Previously, it displayed a 1920x1080 resolution just fine, but then I accidentally changed something in the OSX Display preferences, and the monitor is unable to display 1080p; it only displays resolutions of 1600x1200 and below.

When I select 1920x1080 the monitor displays the message "mode not supported."

I think I messed up by changing the rotation of the external monitor to 270 or something; I tried restoring the default values, but it still doesn't work.

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Have you tried unplugging the monitor from the computer and plugging it back in? Also, can you tell us exactly what you've selected in System Preferences-> Displays for the external monitor? –  Nathan Greenstein May 9 '11 at 0:08
Yes, I've tried that, but it still didn't work. I'm not sure, I think I changed the rotation of the Samsung monitor in the System Preferences-> Displays when it was in 1920x1080 to 270, then it stopped working in that resolution. I also tried reverting back to default rotation, but it still doesn't work. –  radiodio May 9 '11 at 0:09
@radiodio Gotcha. Can you tell us exactly what the settings are that you're using now? –  Nathan Greenstein May 9 '11 at 0:17
@nathan on the Samsung: Refresh Rate is 60hz; Resolution is 1920x1080. edit: I was able to fix it by deleting and Then switching on "Mirror Displays", lowering the resolution, turing off "Mirror Displays", than selecting 1920x1080 again. Thanks for your help, Nathan :-) –  radiodio May 9 '11 at 0:30
@radiodio You should post your solution as an answer to this question so it can help people searching for answers to this problem in the future. –  Austin May 9 '11 at 2:01

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