I have seen a lot of people tweeting about what is going on with Twitte's API status.  Either they think Twitter blocked them, or they are the only app that can't access Twitter.  The truth is that EVERYONE is affected except the few apps that are given priority, ie Tweetdeck.  There are three ways to find out the latest twitter status:

1. Assuming Twitter still loads, go to twitter.com and search for "twitter api".  A quick rundown of the latest tweets should give you a very good indication on what is going on.  This will give you up to the minute status on what other people are experiencing.
2. Go to status.twitter.com for the latest official word on what is going on.  However, keep in mind several hours will go by before they make any new post.  Therefore I suggest using the twitter search method.
3. Follow twitterapi on Twitter.  They post latest API news along with any issues with their service.

Hope this helps.  And be PATIENT, your application will work again soon.  Don't be foolish and hammer twitter with requests or you risk being banned.