See
http://support.microsoft.com/kb/78113, this used to be Q78113 that applied to VFP as well. This known limitation affects any system like VFP that follows IEEE 754, so at least you aren't alone!
Is the data in Oracle? We used to get monster numeric values out of Oracle using strings. If you've already got RVs, first try changing the field type to a c(35) to see what happens- you may be astonished to find it actually works. If that doesn't fly, make the RV against an Oracle View that takes care of the translation to/from a string.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
