There is a better app for downloading Youtube video from your android.It's TubeMate. The app allows you to pause and resume the download.


Market
https://market.android.com/details?id=devian.evan.tmate



You can also download it from the tubemate website.
Go here http://devian7.iisweb.co.kr/download.jsp

But sometimes you can't install downloaded apk files from web.It can be overcome by allowing installation of non market apps in the application settings. For this go to Settings->Applications->Then enable Unknown sources