Typed dataset as remoting methods return type problem

VS 2003 .Net fw 1.1

I have remoting object (singleton) with such method:

public Common.DataSetOffices GetSalesPointList()
{
// prepare return data
DataSet dsResult = m_DataSetOffices.Copy();
return dsResult;
}

I use it in my app as:
...
Common.DataSetOffices dsTmp = obj.SalesPointList;
...
But when ecxecution runs to this string exception occures(just at the
time of assignment operator):

Object reference not set to an instance of an object. System.Data at
System.Data.LookupNode.Bind(DataTable table, ArrayList list)
at System.Data.DataExpression.Bind(DataTable table)
at System.Data.DataExpression..ctor(String expression, DataTable
table, Type type)
at System.Data.DataColumn.set_Expression(String value)
at System.Data.Merger.MergeSchema(DataTable table)
at System.Data.Merger.MergeTableData(DataTable src)
at System.Data.Merger.MergeDataSet(DataSet source)
at System.Data.DataSet.Merge(DataSet dataSet, Boolean preserveChanges,
MissingSchemaAction missingSchemaAction)
at ColIns.DataSetOffices..ctor(SerializationInfo info,
StreamingContext context) in X:\ColIns\Common\DataSetOffices.cs:line
63

As far as I see the problem is in DataSetOffices constructor. But it
is wizard-generated and i dont want to change it for my own. How can
I avoid such problem?