If I set the combobox up with an array i didn't have any problem.

SELECT cTest2
DIMENSION thisform.arrdata2(RECCOUNT(),1)
COPY ALL TO ARRAY thisform.arrdata2 FIELDS TestFld
Thisform.Combo2.RowSourceType= 5
Thisform.Combo2.RowSource='thisform.arrData2'
Thisform.Combo2.numberofelements = RECCOUNT()
Thisform.Combo2.requery()
Thisform.Combo2.ListIndex=300