Excel 97 not saving changes

Once a year we work with large excel spreadsheets containing close to 10000 entries some will have multiple books. Periodically after making numerous changes and saving them to the network the changes do not stick. Office 97 with sp2a and Windows 98. The files are all located on a Novell 4.11 sp6 network. This problem only occurs in excel with one person who is working on large spreadsheets and she is saving the changes.