I had the same problem one day and contacted UW.They said that my internet connection might be down so I contacted my DSL provider and it turned out that the connection was actually down from their end ,just as the UW people said.
My problem was that when I entered my username and password it kept on dialing got to the point where it says setting up interface and after 2 to 3 minutes just came up with an error
I had this problem once when I had to clear my harddrive stored cache on my mac because it was making my internet run slow.. and then it deleted some folder UW made and UW refused to open b/c the folder wasnt there.. So I had to make one up lol.