Sound Is Breaking Up / Popping Or Clicking
When playing back a project, if the audio sounds like it is starting and stopping quickly, it could be because the computer is over tasked due to other programs running at the same time.  In addition, your computer may not be powerful enough to mix the audio.  Always shut down as many unnecessary programs as possible.  It may even be advantageous to temporarily shut down your virus software.  (We do not recommend doing this unless you have done a full scan and are not connected to the Internet.)

Mixcraft has to work harder as it mixes more sounds or processes more effects, especially when time stretching or beat matching

Try increasing the buffer size or the number of buffers in the Sound Device Preferences if your are in Wave mode.  If you are in ASIO mode, try a different ASIO driver or go into the ASIO driver's mixer and increase the latency.  If you are in WaveRT mode, try increasing the latency time.

You can also try freezing a track if there is a lot of effects or compressed audio formats on the track.  (Frozen tracks do not use as much computer power.)

Try setting Mixcraft to conserve CPU mode.  Go to the Preferences and click on Display.  Check the option to use Conserve CPU Mode.

Notice the CPU meter on the lower right hand corner of Mixcraft.  

This will report how much CPU Mixcraft is using compared to the entire computer's CPU usage.

Always make sure that you have the latest drivers for your sound card.  Visit your sound card manufacturer's website to see if there is an update.