Dropping the sound on tracks with X2

I have a perplexing problem. 
Win 7 home premium i7 CPU -920 at 2.67 ghz - 4GB ram- 64 bit os - SONAR X2 Studio
    I was using WDM/KS driver mode, searched the forums and switched to ASIO the problem seemed like it was solved but it came back when I tried to fix dopouts that started again when I loaded an 8 track file I imported from .wav files created in a friend's system where we had been working. I did this to tune the tracks with V-vocal. After this the problem appeared again in a simple two mike track with a video recorded at the same time and imported sync the tracks and video.  I wanted to use Sonar's effects etc.
    
     A few days after I finished tuning the tracks from the 8 track import and sent them off, I was looking at the project just to try mixing it down myself. I saved the project as a separate file first. I am not at all sure what I did, but all the tracks I had not tuned lost all their sound. I tried bouncing to clips and the result was a flat line in all but the two edited clips. Even when I reversed the bounce, the tracks remained soundless. I closed the file without saving, but when I bring it back in the tracks are dead, images only, no sound. To make things worse when I open the original file, or try to open a new project from the raw tracks, they come in dead too, except of course the two files I tuned with V-vocal.
     I am completely baffled at this and have been leary of recording anything of importance or trying to edit anything in my DAW. I just use it a little to record and immediately post to video without edits for facebook and Youtube. Not ideal to say the least.
    This project is safe in my friends system but I can do nothing important with my DAW until I find a permanent solution to this problem.
    

A quick setup question for you. When you are importing files (it seems like you are importing them from another machine), are you using the option "Copy Audio to project folder?"
 
If you are importing from removable media or an online account, or a temporary folder (from say an email download) that you then cleaned, it *will* disappear to SONAR in that case if you unplug the USB or clean out that temp folder. But if you are doing this, when opening the project again, SONAR should be asking you to point it to where the audio is.
 
In addition to the above, it is highly recommended to "Use Per-Project Audio Folders" (Edit->Preferences->File->Audio Data ... the check box at the bottom).
 
Edit: For the dropouts part, using ASIO mode is preferred with updated drivers specific to your audio interface, but I am unclear as to what interface you are using. Can you help us out here?
 

Thanks Brundelfly and Mettelus for answering.
          I am using a mobile pre usb as an interface.
    The raw files are on my computer. I can open them in windows media player individually and they are fine.
     I just checked and see the copy files to project folder box is checked. After they were brought in they played fine for a couple of weeks and I Tuned the two tracks and sent them back. This problem also happens to files recorded into SONAR directly.
     The use per-Project Audio Folder box is checked.
     The tracks are not muted, though I have tried muting them and opening them to no avail.
     The salient bit of information may be when I bounce to clips the lines in the track view they come out completely flat, there is no data there. Somehow the data has been removed and done in such a way that the computer sees the same file in a different context, such as creating a blank project and importing the raw tracks they do not work. I just tried that again with a couple of tracks from the raw data and they are coming in mostly dead, like Billy Crystal says about the guy in Princess Bride. What I am getting there is a quick blip of sound the meter spikes and then silence. It seems wherever I start in the project that is where the blip of sound appears. I hear a bit of Trombone, or a note or two on the guitar and that is all.
      Though I can't rule it out, I doubt it has anything to do with the interface. That seems to be working properly. It is just two inputs Analog to digital with phantom power and some volume knobs.
      If it is drivers. How do I go about updating them? I will look into updating the mobile pre drivers right away.
      It is not a mute/solo problem, rounting or gain, perhaps.
    Thanks,
Arthur