Hello there,
 
Using Sonar 8.0 right now. I record many different things from loud guitar amps to vocals to devices that are directly plugged into an audio interface.
 
I'm recently experiencing a problem where Sonar starts freaking out during playback. This out of control static will come out of nowhere and make the program nearly unusuable. Restarting the audio engine usually fixes the problem but I find that it comes right back. Sometimes I restart the entire program. This always alleviates the issue... temporarily. I can record an entire section, listen back and get the crumbling static, restart the program, and then listen again and it will sound fine. This definitely proves that the recording itself is not the problem, just the playback.
 
Hoping others may have some suggestions for troubleshooting. If it's the sound card, I'm totally willing to buy a new one. I just need to confirm this somehow before spending that money, the last thing I want to do is buy a new sound card and find that it changed nothing.
 
For reference, I use Realtek ALC887-VD2 onboard sound drivers. Never had issues with poor sound quality with any other application but Sonar. Drivers are up to date. I've been monitoring my CPU/memory usage while Sonar is recording and I never go over 50% with either. CPU usually hovers around 15-23% while memory is using less than 50%.

You might check your driver settings / latency under Edit->Preferences->Audio - Driver Settings. 
 
I've also had a similar problem with too much processing going on (even without showing CPU memory usage issues) such as too many Region Fx open, too many high-level processes going on (eg, convolution reverb) that can't keep up with the processing as you play back.

See this for some suggestions:
 
http://www.cakewalk.com/Support/Knowledge-Base/2007013007/Audio-Dropouts-Clicks-and-Pops-When-Playing-and-Recording

MorganT
See this for some suggestions:
 

Thanks for the advice. The second heading in that article "Hard Disk Buffer Size Settings Need to be increased" sounds like exactly the problem I'm having.
 
Unfortunately for me, none of the advice listed in the article worked. I tried increasing buffer sizes in exactly the recommended increments, but it didn't change the behavior of the application. I even tried downloading DPC Latency Checker and monitoring my PCs latency while playing back the project, and even when the playback started crackling, the latency on my PC didn't change at all.
 
So my CPU/memory utilization and latency all checks out. None of the levels change when the application starts crackling. This drives me insane because I literally have to restart Sonar about every 3-5 recording attempts to "clear it up". 

Try disabling all your plugins to see if this kills it.
Also Check your plugins to see if the input/output levels are being overloaded (whilst you are at it levels everywhere else inc pro channel).
 
In a nutshell find where your distortion is coming from...
 
Unrelated but I had the other day where a vvocal clip was inserted. As vvocal was not installed I just got distortion instead.
 
I would also be looking at purchasing something like this, Realtek isn't really quite up to the job IMHO:
http://uk.focusrite.com/usb-audio-interfaces
 

He is running 8.0 so I don't think he has pro-channel, but your other suggestions are good.
 
Also, what are the computer specs?

For reference, I use Realtek ALC887-VD2 onboard sound drivers.
 
That's all you had to say. Sonar is not like Windows Media Player. It needs good ASIO or WDM drivers. Realtech can only run on MME drivers. Option is to install asio4all but that is a 50/50 chance of working right. 
 
Sonar needs a proper audio interface to run smoothly. 
The input jack on your computer has a $2 A/D converter. 
 
 

Cactus Music
For reference, I use Realtek ALC887-VD2 onboard sound drivers.
 
That's all you had to say. Sonar is not like Windows Media Player. It needs good ASIO or WDM drivers. Realtech can only run on MME drivers. Option is to install asio4all but that is a 50/50 chance of working right. 
 
Sonar needs a proper audio interface to run smoothly. 
The input jack on your computer has a $2 A/D converter. 
 
 

Yup. I got my hands on an audio interface and ran through it instead of the sound card and the problem went away. Problem solved, thanks fellas!

Thanks would you mind clicking the answer button below somebodies post.
Cheers...