You might try searching through this thread:

Any way to find dangling references? Thread #1288201 Message #1288201

and this one:

Re: How can I make sure a form is released Thread #1238227 Message #1238261

and:

Clearing dangling references Thread #632799 Message #632799

>Hi
>
>I have a "dangled" reference on one of my forms. There is a lot of code using mappoint, and it is going to take some time to find the problem.
>
>When I try & close down my program after running my form, Visual Foxpro is unable to shutdown.
>
>Is there a way of showing any references left behind in a list?
>
>Any help extremley appreciated