Fixing the issue from an OCX/UserControl seems a lot of work (not impossible, but I don't think it worth the effort).
And I don't know if it is at all possible to show a tooltip from code (I mean to fire the standard VB6 tooltip).
That would be the main obstacle.
The rest is to check whether there are windowless controls with tooltips, and then set a timer and check where the mouse is at every moment, and see if it needs to give a push to some tooltip.

Better call MS for a service pack