There are 2 apps that have been causing me and my friends trouble. 1 is SpringRoll SpringRoll changes icons and images in the ipod. One thing it doesnt tell you is that it makes backups. So when it makes a backup, it adds other images. These images aren't in the code signature. So the apps become unavailable for use. You will get a "this app is not able to open" The second is Toggle SSH.. When i started to use it, my iPod's ip address changed constantly. And it just caused me to restore. Hope this helped.