Tabbing intermittently not working in interop component

[Mike]

I am working on an application originaly developed in VB5.0/6.0 that has a
mdi parent/child forms. I created a VB.net 2003 program with a couple of
forms, compiled it as a dll and registered it as a com interop assembly. I
call this application from a menu item on the mdi parent form in the vb5/6
application. The result is that the user can use my dot net form by selecting
the appropriate menu item from the original vb5/6 program. The problem is
that once in a while, the tab key will quit working. The only way the user
can change fields on the dot net form is to click on the with the mouse. If I
quit and restart the main vb5/6 program and restart it then it will work for
a little while. I found ms article #145566 that seems to be close to my
problem but the fix is not workable in my situation. Any ideas appreciated.
Thanks.