MouseMove fires continuously in VS2005

[Dave]

I have a listview control in a form, and I use the mousemove event (to set a
tooltip). This worked fine in VS2003, but when I ported it to VS2005 I found
that when the mouse hovers over a populated row in the listview the mousemove
event fires continuously - but not when it hovers over an empty part of the
listview. I have duplicated this in a small test program to prove that it's
nothing odd in my software. I don't know if it happens with any controls
other than listview.
Is this known? Is it a bug or a "feature" of VS2005?
--
Dave

[Dave]

Further investigation shows that it seems to be the tooltip that is causing
the problem. If I do not set a tooltip on the control its is fine. If I set a
tooltip then MouseMove fires repeatedly - on the blank are of the listview it
only fires about one every 5 seconds (which is why I didn;t notice it before)
- on the populated rows it appears to fire as soon as the tooltip is
displayed.
This is really wacky, and I can't find any way round it.
--
Dave