Thank you very much for your response Devin,
When it loads it's very fast. I found its not a image loading problem.
Both macs that did not work on Google Chrome were OSX Snow Leopard. On my OSX Lion, at home, it loads fine.
When the bug happens, the images are loaded, but are hidden behind the preloader, and there is "canvas" element missing which would load the grey version of the image.
Links to print screens with Chrome element inspector open:
First Load The site:
http://www.fmprocultura.com.br/wordpress/manual/1.png
Unclicking "visibility:hidden" under ".js_active" on the right column of the inspector shows the images behind the preloader:
http://www.fmprocultura.com.br/wordpress/manual/2.png
Going to another page and returning to the home page loads everything fine, you can see the "canvas" element below the image in the inspector:
http://www.fmprocultura.com.br/wordpress/manual/3.png
I have it working fine on Windows 7 and XP. But my business partner says he gets the bug on a PC on IE and Chrome, not sure which version.
Thanks again guys!!!