External Display Resolution Problem

Hey everyone,

Just a quick troubleshooting question.

I have been using a 20" Acer monitor as an external display with my Macbook Core Duo 1.83. For the last 12 months it was working great;

BUT, I just turned the computer on and in the displays pane I can only increase the resolution to 1600x1200 now, so the screen looks stretched.

Does anyone know how this problem can be fixed?

Thanks

Edit: I was just looking at my iStat Pro and noticed that 1.34gb of the RAM is 'inactive', does this have anything to do with the resolution limit?

 

I understand that there are a lot of threads on MR so I just wanted to bump this up to see if any new users have any idea how to fix this.