SOAP Notification not delivered - "Collection is read-only" - wcf

Question

I'm trying to send a WorkItemChanged notification from TFS to my WCF Service. On my development machine everything works perfectly fine, the notification is delivered (and processed by my programm) almost immediatly.
But now as I wanted to test my software on another system with a "freshly" installed TFS 2012, the notifications are not delivered. I looked into it and found the following error:
elapsed time: 00:00:00.2376893, sql calls: 19, sql connect time: 00:00:00, sql execute time: 00:00:00.1560000, non-sql time: 00:00:00.0816893 (34%), cpu time: 00:00:00.0156001 ( 6.6%), avg connect time: 0.00 ms, avg execute time: 8.2 ms. All methods quick. 0 slowest sql calls: prc_ReadGroupMembership(47 ms) set nocount on
declare #NowUtc as datetime; set #NowUtc=getutcdate()
declare #PersonId as int
declare #rebuildOK as int
declare #PersonN(30 ms) CollectionError: CreateEvent != TransformEvents. CollectionError: CreateEvent != ExpandEvents. CollectionError: AfterReadSubscription != SendNotifications.
There were errors or warnings during notification delivery.
0/0 emails delivered.
0/1 soap notifications delivered.
1 errors.
0 warnings.
-------------------------------
Notification not delivered.
Notification: WorkItemChangedEvent (DeliveryType: Soap; Address: http://localhost:8733/NAMEOFMYSERVICEENDPOINT)
Exception: System.NotSupportedException: Collection is read-only.
at System.Collections.ObjectModel.Collection`1.Clear()
at Microsoft.TeamFoundation.Client.Channels.TfsHttpClientBase.HandleReply(TfsClientOperation operation, TfsMessage message, Object[]& outputs)
at Microsoft.TeamFoundation.Client.Channels.TfsHttpClientBase.Invoke(TfsClientOperation operation, Object[] parameters, Object[]& outputs)
at Microsoft.TeamFoundation.Client.Channels.TfsHttpClientBase.Invoke(TfsClientOperation operation, Object[] parameters)
at Microsoft.TeamFoundation.JobService.Extensions.Core.NotificationJobExtension.SendSoapNotification(TeamFoundationRequestContext requestContext, TeamFoundationNotification notification)
I don't really understand what exactly the problem is or where it comes from. What "Collection" is this error referring to? Is it something on my services side or is it related to a wrong configuration or some missing administrative rights on the TFS's side?
Edit
Almost forgot this question ;)
Well apparently it was caused by an error subscribing to the notification via BisSubscribe.exe. After deleting the notification and re-subscribing, the error was gone.