Reference-Error during sync (Mac OS and alfresco 4.0)

I got this error when starting a manual folder sync:

2015-02-03 16:58:45,282 [Threadpool worker] ERROR CmisSync.Lib.Sync.CmisRepo+SynchronizedFolder [(null)] - Could not crawl folder: /Sites/interludio/documentLibrary/RESOURCES/MEDIA STOCK/IMAGES/Bilder Interludio 02.04.2014
DotCMIS.Exceptions.CmisConnectionException: Cannot access http://srv01.lm-server.de:8080/alfresco/cmisatom/5225254a-d4f8-464b-94a5-e6708dd073f2/children?id=workspace:%2F%2FSpacesStore%2Ff43edf45-b7a2-44d0-a5c9-f61486ec9f49&includeAllowableActions=true&includeRelationships=none&includePathSegment=true&maxItems=2147483647&skipCount=0: Object reference not set to an instance of an object ---> System.NullReferenceException: Object reference not set to an instance of an object
  at DotCMIS.Binding.Impl.HttpUtils+Response.ExtractHeader () [0x00000] in <filename unknown>:0 
  at DotCMIS.Binding.Impl.HttpUtils+Response..ctor (System.Net.WebException exception) [0x00000] in <filename unknown>:0 
  at DotCMIS.Binding.Impl.HttpUtils.Invoke (DotCMIS.Binding.Impl.UrlBuilder url, System.String method, System.String contentType, DotCMIS.Binding.Impl.Output writer, DotCMIS.Binding.Impl.BindingSession session, Nullable`1 offset, Nullable`1 length, IDictionary`2 headers) [0x00000] in <filename unknown>:0 
  --- End of inner exception stack trace ---
[...]

I had to click the manual sync button several times to get the sync process started. Maybe that could be causing the error?

Btw: CmisSync seems to be great piece of Software, i have been waiting for a long time!! Adobe Drive was driving me nuts for years now. Very unreliable and extremely slow. Not usable in production environments. I hope CmisSync will do better. The first impression is very promising.

aegif / CmisSync

Reference-Error during sync (Mac OS and alfresco 4.0) #518