thats the temperature the MB MotherBoard is and yes that sounds hot, but i'm not positive. 40C is still within the normal ranges i think. the reason i say that is because i have an asus a7n8x dlx and my MB temps are 20-25 celcius.
what is your CPU temp and what CPU do you have? and is the room the computer located in hot, normal cool? and how many case fans do you have?