i had the same thing no too long ago. turned out it was one of the nuts on the bottom of the stanchion that had come loose. the noise was the cartridge shifting around the inside and the noise appeared to have traveled up the stanchion, making it sound like its the headtube or headset. check that. i hope its just a minor thing.
"Every gun that is made, every warship launched, every rocket fired signifies, in the final sense, a theft from those who hunger and are not fed, those who are cold and are not clothed.
This world in arms is not spending money alone. It is spending the sweat of its laborers, the genius of its scientists, the hopes of its children."
Dwight D. Eisenhower "The Chance for Peace" 1953