Question marks in memory window

While debugging an application I ran into what seems to be a dangling pointer. When I copy the pointer's address into the memory window in VS2008 (while debugging), I see a bunch of question marks instead of normal data - see attached image.
Does anyone know what that means (i.e. what has happened to the memory)? Am I looking at a section of memory that has been unpaged (if that's the correct term)?

Attachment 30787

Thanks!

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