It could be the phone. I have a 3G that had problems. But I was told to do a restore to factory settings. I did n it still isn't working right. It's basically a mini computer so I have a glitch I can't get rid of. But some apps do have bugs to work out.
If it's an iPhone, try resetting your phone. With the phone on, hold down the home and sleep button at the same time until the phone turns off. This will also turn the phone off. I'd leave it off a few minutes and then turn it back on and see if it will help. If not, check for the latest updates for the phone and app. If it still doesn't work check with apple or service provider for answers.
You will probably have to reset your iPod. Not reset as in turning it off, but setting it back to factory defaults, which will delete EVERYTHING. So put all your important info that is on it on your computer, then go to iTunes and go through the Reset process. if your having trouble with this try going to the apple website, or call apple. You can redownload apps that you bought, for free, so don't worry about that. Reset your iPod to factory Defualts.