Seems like all the time now I get an app off the store that says "unable to purchase" and it'll just sit there, never downloading, and I can't get rid of it. This is unbelievably obnoxious and syncs and reboots won't get rid of it.
I had that a couple of times. Just go onto computer, go on the itunes store, log on to your account, there should be a button that says "download now". Click that button and it will download those apps onto your computer. Than sync your iPod with your computer. It should work.