I've attached some code and test data that demonstrates the problem. The issue boils down to two things, first, assigning an instance of cell to a variable when row=0 and/or column=0 does not throw an exception to sys.stderr. Second, saving a workbook that has had a cell with row=0 or column=0 accessed still completes even though an exception is thrown. In cases where column=0, the entire newly saved workbook is corrupted and cannot be recovered by Excel. Where row=0 an error will be shown by Excel but data is able to be recovered.
Issue #563 resolved