I say this this with a smile. Because I'm hoping that I'm not alone in having the problem you're talking about.
For me it seems like every time I start X2 (and all previous Sonars

) I have some frustrating problem...
The most obvious things are, and you probably checked these, the Audio Engine button and Audio Reset button in the Now time box, and the Input Echo button on the Session Drummer Midi and Audio tracks
Also at the end of one of the posts above is a "related link" about moving Dim Pro folders. I have been looking for that answer for ages....
Good luck with the gremlins