JAPI with MDX query exception

We are using JAPI to query essbase data by mdx, but we have faced a problem:

after the code run to   cv.performOperation(op); It throws an exception. Did anybody face the same problem?

Error: [[[[Z cannot be cast to [[[[I

java.lang.ClassCastException: [[[[Z cannot be cast to [[[[I

  at com.essbase.api.dataquery.EssMdDataSet.init(Unknown Source)

  at com.essbase.api.dataquery.EssCubeView.performOperation(Unknown Source)

  at MDXQ.main(MDXQ.java:48)

import java.util.ArrayList;

import com.essbase.api.base.*;

import com.essbase.api.metadata.IEssMemberSelection;

import com.essbase.api.session.*;

//import com.essbase.api.datasource.*;

import com.essbase.api.dataquery.*;