Button Problem

Hi all!

I have a problem with some of my buttons in my module. I use Lectora Int. Enterprise Edition 2005 SP4a and publish my modules as a CD.

My buttons use .png graphics... one for the normal status, and another one for the mouseover and the clicked stauts.

This works fine for 99% of the buttons, but on some of them the button picture disappears when I move the mouse on the button and I get an "error ping".

Any idea what might be the cause?

Thx!