The first thing to do when you get a database engine error is to reindex. Reindexing is very easy to do. Be sure to close the kiosk Touch-Screen Assistant software—anything that is accessing the data files—and everybody's Reporter except the one which will perform the reindex.
The Reporter creates the indexes all the time. It's how the Reporter alphabetizes and aligns all volunteers. Occasionally the indexes get out of place or corrupted. The Reporter reindex utility can re-sort the indexes and remake them.
We never recommend routine reindexing and we do it only as a last resort, after exploring possible explanations for questions about how the database is performing. We always backup before reindexing.