the application could not be installed on_because it could not be verified

HELP! I download and use free apps all the time, but for paid apps, my mom downloads them off her account, (because you need a credit card) and then I just sync it to my iPod, but for some reason, today I updated "geodefense" and it downloaded no problem. But as soon as I clicked sync and saw the "updating to iPod" the progress bar got to the end and then a message popped up on my Macbook saying that the App could not be installed on my iPod because it could not be verified. So I tried removing it and installing it completely on my iPod again, but the same thing happened and now I don't have the app at all. This is very frustrating for me because it was working fine before and now it isn't.

PLEASE NOTE *** I do NOT have a jailbroken iPod. It is one that I received free from a mac store because my old one had some tech issues with it, so they replaced it.