Ms Access in Multi-tier with ado,Help pls

Delphi6 ent sp2,   win98
server-side is ado + Ms Access, Client-side is DCOM + Clientdataset.
in client-side the clientdataset's fetchondemand is
false,  after connection , seting clientdataset'active true ,so it means
records was downlaoded in client. then for testing the problem ,i
disconnectd with server(dcom_connection is false).
The ploblem is :
if locateing a english record ,it's working well,but when i loacte a
chinese record ,the record can not be found. in fact ,the two records
can be seen in a dbgrid,
such as :
it's good :
ClientDataSet.locate('departmentname','sales',[loPartialKey,loCaseInsensitiv
e])

it's bad :
ClientDataSet.locate('departmentname','??
',[loPartialKey,loCaseInsensitive]) //'??' is chinese string

if i change server-side Ms Access to paradox , the problem is settled

who can tell me why?? how to