Locate dosn't find an existing record in an Access table

Seems that the Locate command does not find an existing record.
I'm using an Access Table, via Microsoft Jet 4.0 OLE db provider,
via an Ado connection and an Ado Table components.

I just open the table, issue the locate command , and it doesn't find
the record.
The search field is the second field of the table (a string).
Other operations (like browsing in  the table) works.

I'm modifying a previous program tha used BDE, and it worked
perfectly.

Any suggestion ?
Maurizio.