I've been looking into the source code and for me it seems there is a bug in the IDisposable implementation in every class which implements it.

.NET Framework Developer's Guide
Implementing Finalize and Dispose to Clean Up Unmanaged Resources
http://msdn.microsoft.com/en-us/library/b1yfkh5e.aspx

I found the following things:

As far as I can see the IDisposable implementations do not implement destructor (~) for finalization.

There is no check if the object has already been disposed

There is no support for object disposing when there is a inheritance hierarchy. Normally this is done by implementing protected Dispose() method as you can see from the link.

Easiest way is just to search for IDisposable or Dispose(). E.g. you can look into Opc.Server which has Dispose() method (which is actually virtual?). I'm not sure but this might be related to the fact that even though I Dispose() all the objects I still receive data updates from the OPC server for the subscriptions.