OCX problem in VB Outlook AddIn

We have developed an Outlook AddIn and we what use an OCX on it. But when we
use an OCX on it, appears an error after we close the Outlook.

The OCX works like we desire. But when we close the Outlook appears a DDE
Server Window error related with memory.

We are using OCX like in following lines.
Dim ocxVar As ClassOCX
Set ocxVar = New ClassOCX
…
Set ocxVar = Nothing

What could be?
Tks,
Rui Oliveira