Smuxi

I tried to send a message to a user who doesn't follow me. After that smuxi crashes with the following Exception:

Inner-Exception Type:
System.Net.WebException

Inner-Exception Message:
The remote server returned an error: (403) Forbidden.

Inner-Exception StackTrace:
at System.Net.HttpWebRequest.CheckFinalStatus (System.Net.WebAsyncResult result) [0x00000]
at System.Net.HttpWebRequest.SetResponseData (System.Net.WebConnectionData data) [0x00000]
Exception Type:
Twitterizer.Framework.TwitterizerException

Exception Message:
<error>Du kannst keine Nachrichten an Benutzer senden, die Dir nicht folgen.</error>

Exception StackTrace:
at Twitterizer.Framework.TwitterRequest.HandleWebException (Twitterizer.Framework.TwitterRequestData Data, System.Net.WebException wex) [0x00000]
at Twitterizer.Framework.TwitterRequest.PerformWebRequest (Twitterizer.Framework.TwitterRequestData Data, System.String HTTPMethod) [0x00000]
at Twitterizer.Framework.TwitterRequest.PerformWebRequest (Twitterizer.Framework.TwitterRequestData Data) [0x00000]
at Twitterizer.Framework.TwitterDirectMessageMethods.New (System.String user, System.String message) [0x00000]
at Smuxi.Engine.TwitterProtocolManager.SendMessage (System.String target, System.String text) [0x00000]
at Smuxi.Engine.TwitterProtocolManager.CommandMessage (Smuxi.Engine.CommandModel cmd) [0x00000]
at Smuxi.Engine.TwitterProtocolManager.Command (Smuxi.Engine.CommandModel command) [0x00000]
at Smuxi.Frontend.CommandManager.DoExecute (Smuxi.Engine.CommandModel cmd) [0x00000]
at Smuxi.Frontend.CommandManager+<Execute>c__AnonStorey0.<>m__1 () [0x00000]
at Smuxi.Common.TaskQueue+<Queue>c__AnonStorey3.<>m__3 () [0x00000]
at Smuxi.Common.TaskQueue+DelegateTask.Execute () [0x00000]