@agussol. Thanks for posting Nicolas. However, you have to give me more info than that. Do you have a link to the page with the listing that I could see?
Also, please bear in mind that I cannot be responsible for how Google Docs Viewer behaves. Sometimes, even when I was testing it, especially with IE, I noticed that it would go blank when loading in the iframe, and then after I clicked the “Open in a New Window” icon in the top right hand corner, it would open up in the new window/tab and then after that it would work in the iframe. Weird.
The fact that it was working perfectly before and you didn’t change anything could mean that it could just be a quirk in Google Docs Viewer. However, I am certainly willing to check it out for you. Either post a link here or send it to me in an email, if you prefer more privacy.