HTML: mouseover and popup bug

[steve.ledger]

Online example

I want to apply a mouseover affect to the
thumbnails which popup a larger image.
I do this by copying the thumbnails
to a ‘mouseover’ layer, then changing
them to grey scale.. But something weird happens when I export..
The mouseover layer is already showing - but worse, they are
NOT in place as they were in the .xar file AND the popups
are no longer where they shoud be!?
What am I missing here ??

Online example