Unmanaged code error message from SSIS? Why?

Hello guys,

Now and then when open my SSIS project (it contains just two big .dtsx packages, 300 tasks both) I get this message:

I don't have any SSIS task -afaik- using old stuff.

It is not relevant because after press several times the dialog box disappears and I can start to work with

I've seen some threads similar this in the past in MSDN:

Thanks for sharing your ideas,