I have the same CM heatsink setup.
Gives me about 38-42 degrees Celsius at nominal load.
and 48-53 degrees at full load.
Make sure u have the Sink fit tightly, and there isnt any direct contact with the processor.
Also check if the heatsink compound has rubbed off..
Go thru the setup instruction again just incase.. i had mounted it the wrong way for instance :-P