There is currently an outage for BIS data for apps and browser in the US across all carriers. BIS email seems unaffected. If you have other connection options for apps, such as BES or TCP, you can switch those and your app will likely work. This worked for me for BerryWeather and Beejive. Some apps like Facebook can't be switched and are not updating properly.
Thank god...I was going crazy wondering what the just-installed DocumentsToGo premium had done to my phone I'd already re-installed FB before I thought to check here.
ETA: Twitter just updated at 12:11 EST, but no FB yet...