Got a weird situation going on!

I'm having a tough time with this one! I load an instance of Dimension Pro. Select a bass sample from "real basses". I play the keys on my keyboard and all is well. Everything is snappy the way it should be, but only for a few minutes. Then without warning I strike a key on my keyboard and the latency is so bad the bass sounds more like a cello with a very slow, delayed response. I changed midi cables, experimented with different buffer settings, (Although I never had to mess with buffer settings before) reinstalled my sound card driver's and made sure Windows is up to date. I finally did a complete install of Windows and Sonar X3. The problem still persists. Any ideas as to what I can try next?

Interface: Scarlett 18i20; Win 7 64 on an AMD Quadcore. All specs in my sig.

Thanks

Thanks Scook. This is a single instance of Dimension Pro (no other tracks/softsynths loaded) with no plugins at all. When pressing a key on the keyboard the response is normal at first but then just turns into mush. Very delayed, slow response.

Just playing. haven't tried turning the audio engine off. I'll give that a try now.

Does this mean the problem went away by itself? (gremlins)
Does this mean toggling the audio engine fixes the latency? (still a problem)

I agree, intermittent issues can be difficult to sort out. Maybe look in the Windows Event log for clues.

I am wondering if there might be some background task that starts itself once in a while, and that happens to spike DPC latency to the point where you get into lag issues with Dimension Pro.
 
Can you check for scheduled tasks?
 
Also, if you happen to be running with a Wi-Fi adapter, these are notorious for spiking DPC latency.  IF you have one present, try looking for a hardware switch or function key to shut it off, just prior to launching Sonar.  If neither are present, then go into Windows Device Manager, find your Wi-Fi adapter, and disable it.  (not uninstall), again just prior to launching Sonar.
 
When you are done with your Sonar session and close Sonar, go back and enable your Wi-Fi adapter again, and all should be fine again.
 
And, since you are running Windows 7 (as opposed to 8), the DPC Latency Checker program can help you determine if your system has some sort of spiking issue that would intermittently cause issues with Sonar.
 
Here is the download (you just run it while Sonar is not running, to let it measure your basic system DPC latency situation, which it scrolls for display):
 
http://www.thesycon.de/eng/latency_check.shtml
 
Bob Bone
 

In all versions from  PE4 on I've experienced situations (mostly with amp sims) where a huge latency suddenly occurs (usually after finishing a take and auditioning), and toggling audio engine on and off makes it go away.

Karyn
If I forget to disable the windows backup before I start Sonar I can work for an hour or so then Sonar suddenly grinds to a halt...

In my case it's just Windows using all the HDD bandwidth looking for things to backup... There are no bugs involved anywhere.

Hmmmm. I think you might have something here. I did see some new files that were added to my backup disk.