Copy items to different farm error for Forms Based Authentication Site

Hi,

I have an event receiver that copies items across web applications in different farms, on the same domain though. This works fine for a destination web app that uses Windows Authentication. The particular one I need to copy to has Claims Based Authentication enabled and throws an error:

System.Net.WebException: The remote server returned an error: (403) Forbidden.
   at System.Net.HttpWebRequest.GetResponse()
   at Microsoft.SharePoint.Client.SPWebRequestExecutor.Execute()
   at Microsoft.SharePoint.Client.ClientContext.EnsureFormDigest()
   at Microsoft.SharePoint.Client.ClientContext.ExecuteQuery()
   at Claims.Event.ItemAdded(SPItemEventProperties properties)

What do I need to do to my code to make this work?