Hi
I have crackling sound when i playback and render sound in a Project. It is random. It kame when i imported a vokal track from Pro Tools. Now it seems that it is there when rendering also. And on the mixes i make.
What can i do about this? Please help me out.

Check you sample rate.  You may want to also check the buffers of your audio device. They could be either too high or to low. 
 
 

The sample rate miss match would make it play slower or faster.so you can rule that out if you are not hearing that. Most likely you are clipping your audio signal or your sound card drivers are set incorrectly for that project.. 
 
Make sure that your dedicated audio sound card has the latest drivers and try WDM and ASIO driver mode at different slider/buffer settings to see what works best for you.
 
CJ

Thanks for fast reply.

Check preferences. . Files... Use twenty four but files instead of thirty two.

I think you got your answer, but I find that I need to go to Preferences | Drivers | ASIO Panel and set my rate LOW (like 256) when tracking to avoid latency.  Then to use Melodyne and to mix, I open it back up and set it to 1024.  I forgot one time to turn it back up and was horrified by the crackling and noise.
 
Note that the scale in that panel has simple digits (like 4, 5, 6) but when you slide to a number, you can see the real number (like 512, 1024) change.  I believe 6 is marked as the default and it usually sounds OK but the lag (latency) when recording is annoying--on my system at least.