Unexpected Existing Transaction With SqlBulkCopy

I have programmatically created a SqlConnection that begins a SqlTransaction.  During the first part of this SqlTransaction, the contents of a table are deleted.  The next part uses the SqlBulkCopy object to copy data from another database (in the form of a DataTable).  The delete goes through fine, but the SqlBulkCopy always generates a SqlException with the message "Unexpected existing transaction."  I cannot think of anything I am doing wrong. 

The code looks at an XML file for instructions on each transaction.  Each transaction is composed of tasks.  Each task will pull data from a different type of database (MVR.Command is a Factory Database object).  Please view the code below and tell me if you can spot what I am doing wrong:

 using (SqlConnection destinationConnection = new SqlConnection(MVR.ConnectionSource.GetConnectionString(destinationServiceName)))
{
destinationConnection.Open();

using (SqlTransaction transaction = destinationConnection.BeginTransaction(IsolationLevel.Snapshot, "Transport"))
{
transaction.Save("Beginning");

int totalTasks = 0;
int successfulTasks = 0;

foreach (XmlNode taskNode in transactionNode.SelectNodes("Tasks/Task"))
{
totalTasks += 1;

string sourceServiceName = taskNode.Attributes["sourceServiceName"].Value;
string destinationTablename = taskNode.Attributes["destinationTablename"].Value;
string query = taskNode.InnerText;

MVR.Command source = MVR.ConnectionSource.GetCommand(sourceServiceName);
source.CommandType = CommandType.Text;
source.CommandText = query;

DataTable sourceData = source.ExecuteDataTable();

try
{
// Prepare the destination table (delete everything)
int rowsDeleted = new SqlCommand("delete from " + destinationTablename, destinationConnection, transaction).ExecuteNonQuery();

using (SqlBulkCopy bulkCopy = new SqlBulkCopy(destinationConnection))
{
bulkCopy.DestinationTableName = destinationTablename;

bulkCopy.NotifyAfter = 1000;
bulkCopy.WriteToServer(sourceData);
bulkCopy.Close();

successfulTasks += 1;

// Log success
}
}
catch (Exception ex)
{
// Log failure
}
}

transaction.Save("End");

// Based on the success of all tasks, either commit or rollback
if (successfulTasks == totalTasks)
{
transaction.Commit();
}
else
{
transaction.Rollback();
}
}

destinationConnection.Close();
}