Opacity animation doesn't show

When I try and animate an objects opacity using a storyboard/doubleanimation the interpolated frames don’t show - the animation runs OK and I can fire the Completed event and catch the output

On screen the control doesn’t fade - it stays at 100% opacity then flicks to 0% opacity when it hits the end of the animation

I’ve actually had this working, but when it was working the control was actually scaling up in size also -

Anyone got any ideas? Kirupa, you use this stuff don’t you?

Can I not see the animation because the client draw area is not being invalidated correctly when there is a change in opacity?

Cheers!