Resolution problems with external monitor on MB

Hey,

I'm currently having a few issues with my MB and my external monitor.

I have a 22" monitor connected to my MacBook, the resolution of the 22" monitor is 1650x1050. When I connect the monitor and the displays manager windows comes up I do not get the option for 1650x1050. But I do for a lot of other resolutions 800x60, 1600x1200 and so on.

I have had the 22" connected to my MacBook for a few weeks now, using both dual screen and clamshell modes. But this stopped working ever since I connected a 19" monitor which uses the resoultion 1280x1024.

I have tried everything I can think of, disconnecting the monitor with the laptop on and then shutting down the laptop and turning it on and then plugging in the monitor. I have also reinstalled OSX and I still have the same problem.

And by the way, the resolution on my MacBook's display is fine and is runiing at 1280x800.

If anyone can help me it would be great thanks .