This issue occurs under version 2.0v1 through 2.0v3
Issue: You will have a broken document if you have used Undo on a Hatch pattern that has one single line segment.
Issue: You will have a broken document if "Show Layers above" is Unchecked while you are viewing some of the layers.
Answer: It is suggested at this time that you do a select all and copy and paste it into a new document. If you need to retain layer information it is suggested that you copy the information over in the following manner.
1. Turn off multi-layer selection.
2. Go to each layer and do a "Select All" and "Group."
3. When completed with #2 above then Select the objects across all layers.
4. Copy everything from the old document to the new document.
5. Close the old document.
Each layer will now be grouped separately in the new document. If you select each group and cut and paste it to the correct layer you will have a new document that is ready for you to work in.
If you think that there will be a issue placing each layer directly over each other, you can paste a point in a given location (for example, X = 2, Y = -2) on each layer. Then when you paste each layer (making sure that everything on the layer is selected, drag by the point to the correct location.