I have the same type of problem.

It is connected to the date time format difference between europe and the usa. I solved it by adding a try/catch statement:

  Public Function CreatedDate(ByVal FileName As String) As DateTime

   Try
---original code goes here
    Catch
    Return Null.NullDate
   End Try

  End Function

  ' Gets the approved date data for a given filename is a folder
  Public Function ApprovedDate(ByVal FileName As String) As DateTime
   Try
---original code goes here
   Catch
    Return Date.MaxValue
   End Try

  End Function

  ' Gets the approved date data for a given filename is a folder
  Public Function Score(ByVal FileName As String) As Double
   Try
---original code goes here
   Catch
    Return 0
   End Try

  End Function