No Tooltips unless form has focus

OK, folks... I know this will sound dumb, and maybe it is (cuz I'm suuuuch a terrible VB.NET programmer)... but I've got a relatively simple applicaiton that dynamically generates a bunch of buttons on a form.  I dynamically associate a unique tool tip with each button.

Here's the problem: The tool tip works (that is, it correctly appears), but only if the main form has focus.  If the form doesn't have focus, I can mouse over any of the buttons, the button properly "highlights", but the tool tip does not appear.

I've tried VB.NET 2005 and 2008, with Framework versions 2.0 and 3.5 -- No change in behavior.

I'm using the "automagic" tooltip class that's associated with the main form... and setting the tooltip within a property "setter" (along with doing a bunch of other stuff) for the button:

                Form1.ToolTip1.SetToolTip(Me, value)
                Form1.ToolTip1.Active = True

A google search shows a couple of other reports of this problem, but no resolutions.

I'm sure there's something simple to fix this... and it turns-out the type of app I'm writing REALLY needs these tool tips to show when the form doesn't have focus.

Any help appreciated,

Peter