In addition, saving when resources are low can cause corruptions. If you notice Word start to slow down noticeably it's always best to quit and restart Word immediately; to close any other applications that are open; and to clear the clipboard, by selecting any character and copying it.
Other signs that you are low on resources: fonts suddenly not displaying properly; the wrong application icons appearing on your Desktop or in Windows Explorer (e.g. Word's icon appearing where Excel's should be). If you get these symptoms, restart Windows immediately.
A corrupt printer driver can corrupt memory; and if you then save, this can corrupt the document. Symptoms: Word often crashes when printing (cure: reinstall the driver).
A corrupt template will corrupt any new documents based on it. A corrupt Normal.dot template is especially bad -- it spreads its evil almost like a virus to almost every new document you create.
If you create list numbering using the Format + Bullets and Numbering dialog, this is likely to lead to a corruption arising eventually, especially if you also have the “Automatically update document styles” checkbox ticked on the Tools + Templates and Addins dialog (less of a problem with Heading numbering than other types).
A bad sector on your hard disk can corrupt a document saved to that sector. Make sure you run Scandisk regularly. Running Defrag regularly will also help reduce the chances of running low on resources. Encourage users to save to the network. Make regular backups..."