Recently I have experienced two ways to loose a whole Maple document (if I had not had a slightly outdated backup copy): 1. Do NOT collaps and expand sections, because it may cause the document to explode in size, but much worse, make it virtually impossible to execute. It seems appaling to me that typographical considerations should destroy a perfectly sound document. 2. Do NOT write something like SubMatrix(Matrix,1..0,1..0), because the 0's makes the line unaccessible, but much worse, it makes it impossible to reload the whole document. I'm using Maple 9.5. Has these fatal errors been corrected in Maple 11?