Boost Python - C++ class' private static data blown away before accessing in Python?

[Stodge]

I've exposed a C++ class to Python using Boost Python. The class,
let's say it's called Entity, contains private static data, which is
an array of strings. Though I think it implements it using MFC's
CPtrArray.

I've also exposed a public function from Entity - let's say it's
called foo. This function accesses the private static data (the string
array).

I have multiple instances of Entity stored in a custom C++ container,
which is also exposed to Python as class EntityList.

In Python, I retrive an Entity from the EntityList:

elist = EntityList()
elist.append(Entity())
elist.append(Entity())

entity = elist.get_at(0)

entity.foo()

But it crashes inside foo() as the private static data is empty; or
rather the string array is empty. I know before that point that the
private static data is valid when accessed earlier by the C++ code as
the program works fine. It just won't work from Python, so somehow the
private static data has been blown away but I can't work out where or
why.

The static data is setup at initialisation - my Python code is only
called long after initialisation is complete.

I added a static dump() function to the Entity class that dumps the
string array, and even if I just do the following in Python:

Entity.dump()

in Python, the private static data is empty. Doing the same from C++
works fine. Weird.

I know this is an impossible question to ask, but can anyone think of
something obvious I need to look into?

Thanks