>I've REINDEXED the file and also INDEXED each key explicitly, to no avail.
Additional test: try deleting all indices. A legal query should work without indices, but might be much slower (let's worry about this later! - this is to test whether the problem is index-related).
Perhaps there is something illegal in your query. Try to eliminate different parts of the query, until it works - or the other way around: add a clause at a time, until you get the error. Then you will know which part is offensive for VFP.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)