mouse button up/down but no clkick

Hi,

I have a user control (a kind of toolbar) which has an owner
draw
button. it does play/pause functionality for displaying
image sequences.
Due to the size of the images the images are loaded in a
background
thread and then marshalled back on to the UI for display.

Now sometimes pressing the button to go from play to pause
fails because
there is no click event fired. We do get (for our overridden
System.Windows.Forms.Button) OnMouseDown and OnMouseUp up
but no
OnClick. We do call the base Button method.

Any ideas why this might be.

adam