I've had the same problem on two Hoyts,and I do not think it is uncommon as I have seen it mentioned here at AT a few times.
With the first bow(Ultramag)I was able to correct the problem myself by spraying a synthetic lube on the top cam axle.The second bow(Ultratech)was not as easy.The lube did not work,but the bow was new so I took it back to the pro shop.They thought it was the limb pockets,so they took down the bow and lubed both pockets.That did not work.Finally they pulled the top axle, lubed it,and I have had no "creaking"noises since.