m_count should match ListView_GetItemCount

[Micah]

Windows XP
wxWidgets 2.6.3
wxListView

When I call wxListView::SetItemCount(...) for my virtual list control I
get an assertion:
m_count should match ListView_GetItemCount

When I step through the code line at a time I can see that
SendMessage(..., LVM_SETITEMCOUNT, ...) is returning 1 (according to
MSDN this means success) but then 3 lines later SendMessage(...,
LVM_GETITEMCOUNT, ...) is returning 0, indicating that no items are
set.

Anyone have any idea why LVM_SETITEMCOUNT isn't setting the number of
items?