>>I could post the code, if anyone's interested, it's not too long (specially if I remove a few non-essential features). I'm not posting it now because I think it's irrelevant; the question I have is whether anyone had this kind of bug, where object members referenced in a collection or array property of another object (of the same class, but not necessarily so) would vanish if they were themselves get manipulated (specially if they were becoming parent objects themselves - even though I had a situation when the bug occurred without that).
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>>Anyone seen a beast of such description?
>
>I have one application that uses a pretty large hierarchy of objects and collections (can be 10s of thousands of objects in some cases) and never ran into anything like you're describing.

Then there remains the theoretical possibility that the runtime is suspect. It's possible that the error happened on workstations where the version of the runtimes may be older (possibly even 9.0 without any service packs, AFAIK). I'll just get the version logged as well and then see which ones had what. Though, that's on the backburner now, since it all works now.