corrupted documents

My name is Sandra Wenz, Helpdesk Coordinator for the Indiana Supreme Court, and I am having a problem with Word 2000, I have several users that when they open up documents from a shared drive, or on their local drive — said documents appear to have boxes where there used to be text?, sometimes they can close the document and open it , and it is corrected, or other times they send it to another user within their office and have them to open it, sometimes this works sometimes it dosent. Has anyone had this problem?.