after ios 5.1 update apps won't download

I had trouble downloading the ios 5.1 update, but found a thread on here that pointed me to an open dns address, so i typed that in the dns field and it worked. I have the updated ios 5.1. I went back and deleted the dns address, connected to my local wi-fi and the internet and all functions seem to work fine, but when i try to download an app, whether it's one i used to have or a new one, it won't download. It begins to, then the icon flashes waiting/loading, waiting/loading, then a screen pops up that says "unable to download application. "imovie" could not be downloaded at this time. done, retry"

It's not just imovie, I've tried others as well.

i turned off and turned on. I can't sync now because i'm away from my laptop. i have verizon iphone 4s.