Converted swf to V8, very strange problems

Has anyone had problems after converting an old swf made with MX2004 to the new version 8 ?

I have a kids colouring board app which has been running live for months.

Here’s a version you can play with: http://www.evynco.com/wboard_resized3.html

Customer wanted a couple of small changes, during which I decided to convert to V8 - as I wanted to use the Drop Shadow feature of V8.

The customer has had components disappearing when he runs on his pc or mac, e.g. one time the pen won’t appear, but it’s shadow will, or a button will be missing. I’ve had other people test this and they’ve occaisionally had things missing too. I’ve tested with Player Versions 5,7,8, & 9.

I know it sounds crazy, a swf is pretty much a black-box, how can it have bits missing when run on other computers ?

Baffled I am. Any suggestions (“take up bricklaying”) will be most welcome.
:sigh: