Created attachment 45687 [details]
simple spreadsheet saved as XLS from 3.3.1
Loaded a simple single-sheet spreadsheet created in LibreOffice 3.3.1 and saved as XLS. (Cell border line width was lost when read in).
Attempting to SAVE or SAVE AS from 3.3.4 Beta1 resulted in "general I/O error" and the application was completely frozen. Had to kill with window's task manager.
Fixing the version.
Apparently also the XLS format contains a ZIP archive somewhere inside, as the fix for bug #36263 made this problem go away, too.
*** This bug has been marked as a duplicate of bug 36263 ***