linq to umbraco error on datefolder type

Hi ,

Has anyone played around with Linq to Umbraco on Blog Package ?

I created two blogposts based on the original blog structure:

( 2009 (DateFolder type) -> 12 (DateFolder type) -> 11 ( DateFolder type)  -> blogpost 1 , blogpost

basically I wanted to get the name of day folder ( the folder which contains two blogpost). So here was my simple Linq query

var temp = from folder in _ctx.DateFolders
                       where folder.BlogPosts.Count() > 0
                       select folder;

Instead of DateFolder object expected , these were the error  I got when I ran the debugger :

base { System.System Exceaption }  :{"Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information."}

LoaderException : {"Declaration referenced in a method implementation cannot be a final method.  Type: 'umbraco.DataLayer.SqlHelpers.VistaDB.VistaDBInstaller'.  Assembly: 'VistaDB For Umbraco, Version=0.1.0.0, Culture=neutral, PublicKeyToken=null'.":"umbraco.DataLayer.SqlHelpers.VistaDB.VistaDBInstaller"}

Any clues? is thig a bug or I just missed something?

P.S : I was following the screencasts  provided on Slace's website about Linq to Umbrco.

Thanks and Merry X'Mas everyone.