felmeddelande vid serialization

Får detta felmeddelande för nedan kod.

File or assembly name qmsb4jks.dll, or one of its dependencies, was not found.

Line 15: Private Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
Line 16: Dim serializer As New XmlSerializer(GetType(poll))
Line 17: Dim fs As New FileStream(Server.MapPath("db.xml"), FileMode.Open)
Line 18: Dim reader As New XmlTextReader(fs)

...
public class pollCB : inherits Page

        Private Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load            
            Dim serializer As New XmlSerializer(GetType(poll))
            dim fs as new Filestream(Server.MapPath("db.xml"), filemode.open)
            dim thePoll as poll = Ctype(serializer.deserialize(fs), poll)
            fs.close()
            ...
        End Sub

End Class

<System.Xml.Serialization.XmlRootAttribute("poll", [Namespace]:="", IsNullable:=false)>  _
Public Class poll
...

Fattar inte vad som är fel, classen poll finns ju. Någon som kan reda ut detta.