Sonar X2 Producer: Files not opening

It could be a coincidence and have nothing to do with the AV software. Try swapping the cable to the external drive. It may be the drive is failing, hopefully there is a backup somewhere. Copy a project to the internal drive and see if it works.

Does that project you copied back to an internal drive have its audio clips within the Audio sub-folder of that project file, or is it possible the audio clips are all back in some common folder.
 
I am just sort of wondering if the project file is looking for the audio from back on the external drive, where there is some sort of timeout being determined by Sonar, in accessing data from the slower drive.
 
I wonder if you would still get that error if you created a simple midi-only project and after saving it, moved it to the external drive and then tried to open it again from the external drive.  This would just test to see if the audio data is at the heart of the issues, in some fashion.
 
Separately, is it possible that Windows is using Selective Suspend to disconnect the external drive?  Windows default behavior will conserve power by 'turning off' idle USB-connected devices, after a certain amount of time.
 
I always modify that behavior in the Windows Power Management advanced options, to disable that feature, as I have USB-connected midi controllers and my audio interface is also USB-connected. 
 
Bob Bone

These are CWP files I hope and not Bundle? 

Try your back up projects first. 
 
You also may need a faster external hard drive. Make sure your har drive spins at 7200RPM or faster. A 5200RPM hard drive is not good! This combines with the sound card you use and the way you have your sound card drivers set will cause drop outs and make sonar glitchy.
 
CJ