Access to XML data with OO4O using Oracle 9i Release 2

[powerrng]

I have some problems to retrieve and manipulate xml data with
OO4O(Oracle Objects for OLE).I create a vb application which send a
SQL statement to the database. I use following code:

Dim mySession As OraSession
Dim myDatabase As OraDatabase
Dim myDynaset As OraDynaset

Set mySession = New OraSessionClass
Set myDatabase = MySession.OpenDatabase("XMLDEMO_HEIPC80442",
"scott/tiger", 0&)


sql = "select extract(e.dfile,'//MachineType[@text=""SM_52""]/CurveType[@text=""presetting""]')
from xmltest e"

Set myDynaset = myDatabase.CreateDynaset(sql, 0&)
....

In the last call, CreateDynaset(), the application breaks down with
Error 04976 -> Creating OraObject instance in client-side object cache
has failed. What can I do? Did I
forget some paramaters which I have to be set?