Problem getting a CAPI:TREE-VIEW with :CHECKBOX-INITIAL-STATUS to work on Windows XP.

Hi,

I'm trying to use a CAPI:TREE-VIEW to select which items of a 
hierarchical dataset should or should not be processed.  I want to show 
a little bar next to each item to indicate what percentage of its 
children are selected.

I've got all of this to work, but when I tried to use 
:CHECKBOX-INITIAL-STATUS to make the tree-view's bars reflect a 
predetermined set of selected items upon creation, things broke down. 
The bars of the roots show the calculated percentages nicely, but when I 
expand any of them I get an error about the undefined function 
CAPI-WIN32-LIB::HCHILD being called in 
CAPI-WIN32-LIB::EXPAND-TREE-VIEW-ITEM.

Loading the attached source file and evaluating
(capi:display (make-instance 'tree-view-test))
should be enough to reproduce the error I'm getting.

Is this a bug?  Am I doing something wrong?  Does anyone know a fix or 
workaround?

Thanks in advance for any help.

Regards,
Dirk Gerrits