See <http://blogs.msdn.com/b/oldnewthing/archive/2012/06/08/10317022.aspx>. The EXCEPTION_IN_PAGE_ERROR exception can happen when you read, write, or execute memory in an invalid page. In nsZipArchive.cpp we're recovering from all scenarios, but we should only recover from reads since as far as I can tell that is the only legit thing that this code might be doing with the mapped pages, and if it is writing to or executing something from such pages, it's better to crash than to recover from it.