OK there's a few things to check on a CX.

1. Check the linkages on the lower head make sure the metal or plastic nubs sticking out are inside the linkages. The lower head is actually 2 pieces not just 1 sometimes the screw loosens and the lower head moves a little bit and the nubs pop out of the linkages.

2. Verify the top head does not move up and down when you pull up on the flybar, this indicates the pinion and gear below the chopper are not in full alignment.

3. Try to see which blade is spinning slower if at all possible to isolate futher which blade is having issues.

4. Check your motors by unplugging (note the old location and cable orientation) one of the blades and throttling about 3/4 up, see if the blade is wobbly, slow,etc...

5. Repeat for other motor.

6. Replace motor if bad, maybe replace both at this point.

7. Look for extreme vibration, could be bent shaft. Look at all pitch linkages verify they are are attached. Check your flybar to top blade linkage and make sure the head head has not come off.

8. Check the servos do they move up down when you give input.

9. Verify that you do not have full proportional set on the reciever, this should not affect actual flight, but may help explain the spinning. You could have a mix of issues, set this back to 50% and begin troubleshooting this.

10. Check the pitch linkages to verify they are not too long/too short. One blade may have too much pitch.

11. Check the swash plate does it move other than up/down left right on the shaft, it should not spin.

12. Remove the blades and verify the nubs are still there that hold the blades on, these are easily broken on the stock plastic heads.

I'd say the best course if this doesn't help is taking it to the LHS for help, they'll be more than happy to help, especially if you at least buy some blades or something.