Focusrite Scarlett 2i2 with Sonar 8.5.33 on i7 Pavilion laptop 16 RAM. The Scarlett driver is set as the Timing and Playback Master and running in WDM mode. No more than two audio tracks are running.
 
Crackling:
Crackling is loud, consistent and persistent at all times during playback.
 
Late:
The cursor is well past the data before the audio is heard, perhaps as much as a quarter note at 120 bpm. 
 
Thanks - rev
 
 

Are you using WDM because there are no ASIO drivers ( 64 bit) ? Cakewalk recommends you try both to see which works. If a company does not update the drivers then you are sometimes faced with also upgrading the interface. 
Also have you run the DPCLAT latency test? Laptops are problematic and if there are red spikes you need to deal with that first before using that computer.  

You definitely want to be using the 2i2 in ASIO mode for best performance.  Changing Sonar to use ASIO will most likely clear up the issue.  If it does not, it would be a good idea to make sure you are using the latest drivers.  If those do not help, there are some Windows settings outlined in this article that can have an effect:
For Win7:
http://us.focusrite.com/answerbase/optimising-your-pc-for-audio-on-windows-7
For Win8:
http://us.focusrite.com/answerbase/optimising-your-pc-for-audio-on-windows-8
 
If you continue to have issues as Cactus Music mentioned, it could be a DPC latency problem.  For more on DPC latency:
 
http://www.thesycon.de/deu/latency_check.shtml
 
If you continue to have trouble after trying the above, please contact Focusrite support using this link:
 
http://us.focusrite.com/answerbase/contact

Thanks to both of you - I will read all the links, take all the steps and get back to you. 

I did the optimization but it shouldn't be necessary on an i7 machine with 16 RAM. I ran the latency util and it was all in the green (good) with a red bar reaching to the second line occasionally. I made screen shots but I'm unable to attach images because that feature on this site isn't doesn't seem to be working. 
 
 
The message from the latency util was 'Cool, should be able to stream audio and vid with no dropouts' then it changed to 'some drivers are behaving bad (not my grammar) on this machine, use Device Manager and Disable drivers one-by-one to find the misbehaving driver.'
 
We're really not talking about misbehavior, we're talking about totally unusable. The focusrite driver makes everything sound like it's underwater. The native HD audio driver also has clicks when running Sonar and the cursor is well past the data before you hear the notes. 

The DPC test you ran confirms that it is not the Focusrite driver, but DPC latency issues that are preventing the audio from being reproduced correctly.  Red spikes on the DPC test are indicative of a problem.  Also, were you playing back or recording audio while running that test?  To properly test for DPC latency, you need to reproduce the scenario in which you are having the problem (ie. playing back audio).  If you were not doing this previously, I would wager that you will see a lot more spikes if you test for DPC while reproducing the audio glitches.  Either way, from what you have described, it sounds like there is a DPC problem that needs to be resolved in order to stop the audio quality problems.  The same link that you downloaded the DPC checker from also has a lot of background information on DPC and what it is, as well as instructions for resolving DPC latency problems.

I wasn't playing back audio at the time, didn't know to do that so I'll try that tomorrow. Thanks, I'll post back.

The spikes will happen on a 2004 P4 with 1 Gig of RAM or on an 2013 i7 with 16 Gigs of RAM.
 
Laptops are problimatic. Most times disabling a few backgounds processes will do the trick.
Wireless and then Battery managment are biggies.
But some laptops will still create spikes even after every known tweek has been performed. The problem might then be in the BIOS itself rendering the laptop useless for audio, It does happen.

>rendering the laptop useless for audio
Yeah, this is hugely disappointing, I bought the laptop for the sole purpose of doing audio on it. I even posted here for a recommendation before I purchased but no one had a suggestion. So I took the plunge and then bought the Focusrite interface so I'm down $1,000 and it's all looking useless.
 
I tried the tweaks (no change after disabling wireless) but couldn't get rid of three spikes per screen running dpclat. Then I ran the RATT util (despite the fact that it 'doesn't to work on x64 systems.' The report didn't give me a summary per driver - I just got one result for "Unknown."
 
There were a huge number of DPC calls but since no driver was named, the report was of no help. I didn't think of battery management so I'll try that next but it's not looking good. 

What's different about desktops?
 
Or a better question: Why can the machine play all audio files outside Sonar but not inside Sonar? The native 'High Definition Audio Driver' is fine playing a wav file from the desktop, why does it not work playing the same wav file is inside DAW software?  And why is the High Def Audio Driver working 10 times better than the Scarlett driver made for the purpose?