The remote server returned an error: (401) Unauthorized.
There are many reasons an error like this can happen. What kind of debugging have you tried?
I’m having the same issue with both LINQ to Twitter and Twitterizer (tried both to see If I could get some success)
Solved the same problem :
If your application is of type “browser” then you need to specify ‘proper’ callback url in application’s settings
are you sure? That by specifying call back url, this error will be removed?