I'm on an iMac Core Duo 20" running at 1680x1050 and I recently purchased a Dell E207WFP (http://accessories.us.dell.com/sna/productdetail.aspx?c=us&l=en&s=dhs&cs=19&sku=320-5123) and notice it says it supports 1680x1050. Also, I use this Dell monitor with my PC when I'm not using my iMac and sure enough, I run 1680x1050 . But for some reason when I set up the Dell as a second display in system preferences if I choose 1680x1050 the monitor turns black and flashes the message "Cannot Display This Video Mode... Optimum Resolution 1680x1050 60Hz" (and yes, I choose 60Hz as the refresh rate). Does anyone have any idea as to why this is happening, it would be greatly appreciated. Thanks.