Whenever I land or move around Zürich, New York or Chicago, I get a "This computer has run out of available memory" message. Only on these 3 airports. I wonder if it has anything to do with the special features you use.
If you had the issue at JFK only, it might have been related to the special features, because JFK is the only one that *really* has "special" feature, up to a point to requiring a separate module for it (the Couatl Python engine).
But KORD and LSZH, they don't really do something special that might lead to a memory exhaustion. Most of the work is done via Simconnect and, the few bits that Simconnect do not supports, are just writing a couple of value in memory, but there aren't any explicit ram allocations. If the write to memory was wrong (and it's not), FSX would simply crash, instead of giving an memory exhaustion message.
There's are several discussions on Avsim about the PMDG MD-11 OOMhttp://forums.avsim.net/dcboard.php?az=show_topic&forum=121&topic_id=456054&mesg_id=456117http://forums.avsim.net/dcboard.php?az=set_linear_mode&forum=136&page=&topic_id=156477&prev_page=show_topic
Which doesn't mention our sceneries. So, I think that the airplane simply takes too much memory, forcing probably to enable the /3GB switch. It might have happened with any other complex scenery or addon, like AI packages, etc.