Sometimes YES, sometimes NO

[Tonatiuh]

This is my SELECT statament:

SELECT DISTINCT(contrat.rsocial) FROM contrat,contra _
WHERE contrat.rsocial=contra.contrat _
AND contra.centro IN _
(SELECT centro FROM derechos _
WHERE usuario='MyUser')

Sometimes returns me values and sometimes returns EMPTY !!!!

I'm using VB6 with VFP as database in WIN98.

Any idea will be deeply appreciated.

Thanks!