This already happened twice in the lab so I know it will come back to haunt this lab again.
Whenever you open up a recent saved network and see BLACK areas in the place where the CT/MRI source image data used to be in, there are TWO possibilities:
1) If you see PARTIAL original source data then this signifies a saving corruptions issue. The most likely cause is the disk full and no more space to save. When this happens, you need to STOP WORKING and do NOT CLOSE anything and immediately start cleaning out junks and old useless networks out so you can SAVE!
2) If you see TOTAL darkness and no original source data whatsoever. Then your source data is NOT connected/lost. Eg. "OBELIX" is usually connected with "OBELIX-label" data module. If you do not have OBELIX data module, the label will still show up but the background MRI/CT source data is lost. In that case, if the label file is still working, then you have not really lost anything because the source data are easy to recover. Just load from a previous version of the save and load only the source data from there and click on the little "white" square option of the label file and link up to the reloaded source data and you will be good to go.
HOWEVER, note that when you produce surface generation, you are NOT using the source data. The surface generation is really based on the label that has been produced.