Below are the first four things to do to re-index a file from the Support Knowledge base:
What to do when your file is corrupt
1. With the database open, choose File menu > Manage > Database.
2. In the Manage Database dialog box, click the Fields tab, and double-click the indexed field.
3. In the Options for Field dialog box, click the Storage tab.
4. Remove the index by selecting Indexing: None. Then click OK.
The next four steps are the same except that in step four you clik All to re-create the index
-except it didn't work for me. When I go to restore indexing I find it did not move to "None" in the first place, even though I had saved and closed the file before returning to restore the indexing.