I can send fine from the Newsletter section in the backend, however if I try to send from a content node I get the following error when I click "preview"

Any idea?

Server Error in '/' Application.

Sequence contains no elements

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidOperationException: Sequence contains no elements

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace: 


[InvalidOperationException: Sequence contains no elements]
   System.Linq.Enumerable.First(IEnumerable`1 source) +514
   System.Linq.Queryable.First(IQueryable`1 source, Expression`1 predicate) +490
   NewsletterStudio.Services.RenderTasks.Tasks.FitIntoTemplateRenderTask.ProcessPreRender(RenderResult renderResult, RenderTaskParameters parameters) +706
   NewsletterStudio.Services.RenderTasks.RenderTask.ProcessPreview(RenderResult renderResult, RenderTaskParameters parameters) +15
   NewsletterStudio.Services.RenderTasks.RenderEngine.RenderPreview() +302
   NewsletterStudio.External.NewsletterRender.Page_Load(Object sender, EventArgs e) +1267
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   System.Web.UI.Control.LoadRecursive() +71
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3178

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.17929