Problem installing ad-hoc app on iphone: "resources have been modified."

We had the same problem during our first Beta. Someone on Windows dug in the xxx.app folder then Explorer created a Thumbs.db file inside and, boom, he got the message "The application XXX was not installed on the iPhone "YYYY" because its resources have been modified." when he tried to install.

He had to remove the app from iTunes, deleted all the Thumbs.db from xxx.app and then it worked.

We finally got rid of the problem. We were trying to include an image for iTunes after creating the build, but when we used this method (http://iosdevelopertips.com/xcode/itunes-icon-for-ad-hoc-distributions.html) everything went smoothly.