Here is a fix that works for me...

/// <summary>
/// Fetches the full branch name for the relative branch name
/// </summary>
private string GetFullBranchName(string name)
{
string branch = null;
try
{
m_browser.ChangeBrowsePosition(OPCHDA_BROWSEDIRECTION.OPCHDA_BROWSE_DOWN, name);
}
catch
{
// if we can't get to the branch then something is wrong
return null;
}
try
{
m_browser.GetBranchPosition(out branch);
}
catch
{
// If something goes wrong then we still need to get back to where we were
}
m_browser.ChangeBrowsePosition(OPCHDA_BROWSEDIRECTION.OPCHDA_BROWSE_UP, "");

return branch;
}

/// <summary>
/// Fetches the element names and item ids for each element.
/// </summary>
private ArrayList FetchElements(EnumString enumerator, int maxElements, bool isBranch)
{
...
// create new element objects.
foreach (string name in names)
{
BrowseElement element = new BrowseElement();

element.Name   = name;
// lookup item id for element.
try
{
  string itemID = null;

  if (isBranch)
  {
    itemID = GetFullBranchName(name);
  }
  else
  {
    m_browser.GetItemID(name, out itemID);
  }

  element.ItemName    = itemID;
  element.ItemPath    = null;
  element.HasChildren = isBranch;
}
catch
{
  // ignore errors.
}

...

Changed code to:

BrowseElement element = new BrowseElement();

element.Name = name;
element.ItemPath = null;
element.HasChildren = isBranch;

try
{
string itemID = null;
m_browser.GetItemID(name, out itemID);
element.ItemName = itemID;
}
catch
{
element.ItemName = null;
}

elements.Add(element);

Will be part of Release 2.00.101