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Dieter Maurer wrote Just a wild guess: is the GC guaranteed to be thread safe?

Yep. The GC is _almost_ certainly not the problem here - it's just that the GC is the poor bunny that has to walk through the objects in memory. So when something's been mangled, the GC is the thing that falls over and breaks. I think I've mentioned it before, but looking at the object _before_ the corrupted one in memory might be a useful thing to try... Anthony -- Anthony Baxter <anthony@interlink.com.au> It's never to late to have a happy childhood.