Problem updating a large binary field (PostgreSQL, ODBC, VC++)

Hello,

I created a table where a record consists of a single field of type
lo. I'm trying to add a new record and store the contents of a file in
it. However, when I call CRecordset.Update() I get the following
exception: "SetPos with data_at_exec not yet supported". My table
doesn't get updated.

Environment: PostgreSQL 7.4.1 on Cygwin, Visual C++ .Net 2003, ODBC
driver 3.520. I pasted my code below (the line that causes the error
is marked). Anyone knows why it doesn't work, and if there's any other
way to do what I want?

TIA,
Pavel

CDatabase db;
CMyTable table(&db);
table.Open();
char* FileName        = "c:\\test.txt";
CFile f;
CByteArray ByteArray;

if (f.Open(FileName, CFile::modeRead, &e ))
{
  CByteArray ByteArray;
  long size = f.GetLength();
  ByteArray.SetSize(size);
  BYTE *p = ByteArray.GetData();
  ZeroMemory(p, size);
  long result = f.Read(p, size);

  table.AddNew();

  if(!(table.m_data.m_hData))
  {
    ::GlobalFree(table.m_data.m_hData);
    table.m_data.m_hData = GlobalAlloc(GMEM_MOVEABLE,size);
    if(table.m_data.m_hData) // GlobalAlloc could return NULL...
    {
    table.m_data.m_dwDataLength = size;
    LPVOID p2 = ::GlobalLock(table.m_data.m_hData);
    memcpy(p2, p, size);
    ::GlobalUnlock(table.m_data.m_hData);
    table.m_data.m_dwDataLength = ::GlobalSize(table.m_data.m_hData);

    // mark the record for the update
    table.SetFieldDirty(&(table.m_data), true);
    table.SetFieldNull(&(table.m_data), false);
    }
   else
   {
        AfxMessageBox("Couldn't allocate memory");
   }
}

table.Update(); // <-- THIS DOESN'T WORK!