i am playing videos on our club plasmas and projector and the resolution is terrible ( dark and grainy). i am using a macbook pro w/3g ram 2.4g intel core 2 duo processor. I use the mac video adapter to an rca adapter into a coaxial cable

I believe the converters you are using is what is causing the issues.

Do you have a new Mack Book Pro - the new ones with the Mini Display output? Are you using the Midi Display to VGA and then going to something that converting it to RCA and then you are going to something else that converts is to coaxial?

I am using an older macbook pro (new last year before the current model) the converter i am using is the "apple DVI to video adapter" then the coaxial cable has an RCA adapter on the end of it.

The Co-axial cable is the one distorting the signal. I would recommend using a powered converter that will accept the adapters connection and give you a Co-Axial connection.