Corruption in Excel when saving

This has happened twice already with two different users. User has spreadsheet open makes the changes and saves to network drive. Before Excel has a chance to fully save document an error appears and Excel closes automatically. Do not know what the error is, cannot duplicate action. When the user tries to reopen the document a window appears stating "File cannot be found" with a title of Microsoft Visual Basic in the title bar. Has anyone seen this before and if you have was it resolved?