This is a weird one. Occasionally Sonar X2a stops on play back and record. It starts up OK when I press the start button. I did have a white other day (no jokes please), but unlike the old days, Sonar sorted itself out. I just waited. I am using a Sapphire 40 Pro with 3.1 drivers. It makes no difference which drivers I use, I still get the occasional stop. Using Windows 7 ultimate 64 bit on an AMD Quad core with 8 gigs ram.
I love X2 and this stop doesn't impede my work flow.
Any ideas out there
Happy new year to you all

Are you using any kind of control surface or are you just using the keyboard and mouse?  Wireless or hard wired?
 
You may be getting into dropouts and have your warnings turned off.   Have you tried increasing your buffers to see if that makes a difference? 

You've probably nailed gcolbert. I have tune up utilities and my antivirus on. Together they'll form a formidable team.

Are you using any freebie VSTs? 

Check the Windows Task Manager to see if you have another program that's using a lot of CPU. 

No daveny I use Cakewalk, Native instruments and Tassman plugins, howerver, I think uplugging my internet link has come up trumps. I has never affected Sonar before, but I guess it should be common practice to pull the plug out. All my friends. I'm do