These were just tracks my client recorded in another studio and burned as an audio disc. This problem seems to have just popped up. I have done this before into X2a without problems. Dave, I did install the program to C: but my Sonar audio files are on another drive. Do you think a clean install is in order? I have to admit, it has seemed rather buggy to me, nothing major, just little things like not being able to quick group in the console view that fixes with a program restart. A few things like that.

Any way, thanks for the helpful suggestions gang. I've been at this for most of the day and it has been a real work killer!

These were just tracks my client recorded in another studio and burned as an audio disc.

Hmmm. Is it possible these are copy-protected or encrypted to keep someone from copying them? 

If you look at the disk in Windows Explorer, what are the full filenames, i.e., Track01.cda or xxxxxx.wav or xxxxx.omf? 

Can you play the files in Windows Media Player? 

Try importing files in X2A from a commercially available CD.  Does that work? 

I suspect its something to do with the files although I don't know why it works with Sonar 8.5 and not Sonar X2A. 

Before you do a full uninstall / reinstall of Sonar, I would just do a reinstall in place (over the existing version).