About SQL execution plan change, which related to JDE invoicing

Hey, there,

I just have a question about the following query inside a database that supports JD Edwards EnterpriseOne product. Has anyone see a similar SQL query like the following (from Service Billining):

SELECT * FROM F4812 WHERE ( WDICU = :KEY1 AND WDDOCZ = :KEY2 AND WDDCTI = :KEY3 AND WDKCOI = :KEY4 AND WDSFX = :KEY5 ) AND ( ( WDCO = :KEY6 OR WDCO = :KEY7 OR WDCO = :KEY8 OR WDCO = :KEY9 ) ) ORDER BY WDICU ASC,WDDOCZ ASC,WDDCTI ASC,WDKCOI ASC,WDSFX ASC

There is an index F4812_2 on (WDICU, WDDOCZ, WDDCTI, WDKCOI, WDSFX) precisely.  It used to use index F4812_2. BUT, it suddenly stopped using it and started table-scans. If you have encountered similar issues, could you please help a bit.