Then index is created internally by VFP because of / IN (select field_expression..../.

Probably the length of the field_expression is not determined properly from the very first record. Try to use something like padr(field_expression,...) to have its length constant. If it should be numeric, then try:
00000000000.00 + field_expression

>My original message did mention that I blew away ALL of the indexes.
>
>Response: No index expression available.