Releasing a shared viewmodel using the MVVM plugin

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C#

C#4.0

MVVM

Silverlight5

Hello,

I was wandering how you'd release a shared Viewmodel using the MVVM plugin.
I have a tabcontrol with several tabs sharing the same viewmodel. So, I have:

[PartCreationPolicy(CreationPolicy.Shared)]

When I move across tabs, I don't release the shared Viewmodel but when I close the entire tabcontrol, I want to be able to completely release the Viewmodel.
The following code line no longer releases my viewmodel:

PluginCatalogService.Instance.ReleasePlugin(DataContext);
    DataContext = null;

Does the ReleasePlugin(DataContext) apply to a Shared Viewmodel as well?
I thought I had this working before I upgraded to the released version of Silverlight 5 and Galasoft MVVM SL5

Thanks!