Karma,
Delete your AUD.INI file and let Sonar rebuild your settings.
Should be in C:\Users\Your Name\AppData\Roaming\Cakewalk\SONAR Platinum
You can rename the existing file AUD.OLD, I just delete it; you can't hurt anything.
You will lose any "friendly" names for ins and outs, so make note of how things are setup now.
Its a "simple" text file and I've compared before/after and other than the "order" of things it always looks the same.
That being said, if I'm having "issues", this always seems to sort it.
Placebo effect?
Or could just be your buffers are set too low.
HTH,
Tom