I highly recommend you call your local support. One possibly bad cam project will not break or mess with any other cam projects. So you don't have to worry about your other projects. You can start by trying a reinstall over your existing install to see if a file has been corrupted. It will prompt you to repair your previous setup. The other thing I would try is to clean out your temporary folder. to do this, first locate your temporary folder by opening your CAM SETTINGS > CAM-PART > CAM-PARTS TEMPORARY FOLDER. Note where it is pointing. Go to that folder and create a new folder and place all the contents of the CAM-PART temporary folder into the new folder you created. Now try opening a cam project a different cam project to see if it opens.
All sorted, it seems the hard drive that the temp folder was in was getting a bit "full" moved the temp location to a new drive and solidcam works great now.