Unable to update unidata from .NET - unidata

Question

I've been attempting for the last couple of days to update unidata using sample code as a basis using .NET without success. I can read the database successfully and view the raw data within visual studio. The error reported back is a out of range error. The program is attempting to update the unit price of a purchase order.
Error:
{" Error on Socket Receive. Index was outside the bounds of the array.POD"}
[IBMU2.UODOTNET.UniFileException]: {" Error on Socket Receive. Index was outside the bounds of the array.POD"}
Data: {System.Collections.ListDictionaryInternal}
HelpLink: null
HResult: -2146232832
InnerException: null
Message: " Error on Socket Receive. Index was outside the bounds of the array.POD"
Source: "UniFile Class"
StackTrace: " at IBMU2.UODOTNET.UniFile.Write()\r\n at IBMU2.UODOTNET.UniFile.Write(String aRecordID, UniDynArray aRecordData)\r\n at ReadXlsToUnix.Form1.TestUpdate(String PO_LINE_SHIP, String price) in c:\Users\xxx\Documents\Visual Studio 2013\Projects\ReadXlsToUnix\ReadXlsToUnix\Form1.cs:line 330"
TargetSite: {Void Write()}
failing Test Code is:
private void TestUpdate(string PO_LINE_SHIP,string price)
{
UniFile pod =null;
UniSession uniSession =null;
//connection string
uniSession = UniObjects.OpenSession("unixMachine", "userid", Properties.Settings.Default.PWD, "TRAIN", "udcs");
//open file
pod = uniSession.CreateUniFile("POD");
//read data
pod.Read(PO_LINE_SHIP);
//locking strategy
pod.UniFileLockStrategy = 1;
pod.UniFileReleaseStrategy = 1;
if (pod.RecordID == ""){
pod.UnlockRecord();
}
//replace existing value with one entered by user
pod.Record.Replace(4, (string)uniSession.Iconv(price, "MD4"));
try
{
pod.Write(pod.RecordID,pod.Record); //RecordId and Record both show correctly hover/immediate window
//pod.Write() fails with same message
}
catch (Exception err)
{
MessageBox.Show("Error" + err);
}
pod.Close();
UniObjects.CloseSession(uniSession);
}
}
Running on HP UX 11.31 unidata 7.2 and using UODOTNET.dll 2.2.3.7377
Any help greatly appreciated.
This is the write record version and have also tried writefield functionality with same error.
Rajan - thanks for the update and link. I have tried unsuccessfully to read/update my unidata tables using the U2 Toolkit. I can however read/update a file I have created within the same account. Does this mean there is a missing entry somewhere VOC, DICT for example.