Dynamically Loading .NET Assemblies

I am writing a program and want the program to support plugins. I have created an interface that the program should implement. I am using the following code from my main program to call the plugin:

Dim asm As Assembly = Assembly.LoadFrom(ff.FullName)
' Get the type
Dim myType As System.Type = asm.GetType(asm.GetName.Name + "." + asm.GetName.Name)
' If the type is null then we try again without the root namespace name
If myType Is Nothing Then myType = asm.GetType(asm.GetName.Name)
' Check to see if the plugin implements the required Interface
Dim IsMyPlugin As Boolean = GetType(LGInterfaces.ILGSQLPlugin).IsAssignableFrom(myType)
Dim ActivePlugin As New PluginObject()
If IsMyPlugin Then
    ActivePlugin.Plugin = CType(Activator.CreateInstance(myType), LGInterfaces.ILGPlugin)

      

        
        
        
      

    

Everything works and I can access my exposed properties except for one problem that I can't figure out. In my plugin, I am using the following code to expose the property:

Private m_PanelObject As Windows.Forms.Control

Public Property PanelObject() As Windows.Forms.Control
Get
     Return m_PanelObject
End Get
Set(ByVal value As Windows.Forms.Control)
    m_PanelObject = value
End Set

      

        
        
        
      

    

Ok, so I set this property from my main program and everything works. Except that after a while, m_PanelObject gets Nothing for some odd reason. I don't set it anywhere in my program, and there is no place in the plugin code that sets it to Nothing. So what am I missing here? I'm sure this will be pretty obvious. thanks in advance