Aborted download of an app on the iPod. Will I be charged again to get it?

I downloaded an app yesterday, and it lasted a very long time. I don't know why, but the download started again from scratch a few times, then I got an error message saying it was not possible to download it on the Ipod touch and I got to do it through my computer.

OK but the price of the app has already been deducted once, and when I go to ITunes on my computer it asks me to buy it again.... what should i do ?

Thanks for the answers.