Hello Phil and Tom, I think I can help you with my reply. I have a Macbook Pro 13" middle 2010 and last week I have purchased an external monitor Dell U2412M, the same as you, and I had the same problem as you, I cannot select the maximum resolution of 1920x1200 and the fact is that the solution is very easy:
- Connect the MBP to the external monitor through the cable (I have miniDP to DP but you can also use the DVI cable if your MBP has this connection).
- Connect the MBP to the MagSafe and the MagSafe to the power (this is very very very important, believe me).
- Turn on the MBP and in the System Preferences you must select "mirror" or "duplicate screen" or somethig like this (I have my Mac OS X Lion in Spanish language, sorry). When you do this the external monitor shows the same as the screen of the MBP but with a poor resolution, because it gives the maximum resolution of the MBP.
- Now you must close the screen of the MBP. The Dell monitor then will turn blue a little moment, you must press any key of the keyboard or the mouse or the trackpad and then you could use the full resolution of the Dell U2412M with our loved MBP.
I hope this will help you both and future people. Regards from Spain.
