Can't load custom httphandler over multiple projects

in my solution i have a couple of projects.

At my Allgemein.dll (General.dll) i have a custom httphandler which looks for pdf's and does something with it.

At every project in my solution i include the Allgemein.dll.

Now if i'm logged out of my application and i call a pdf, my httphandler works great. But if i'm now login to my application and call a pdf, i got the following error: "The type "Allgemein.Handlers.FileProtectionHandler" in the assembly "Allgemein" could not be loaded."

What i'm doing wrong?

My web.config

<httpHandlers>
      <add path="*.pdf" verb="*" validate="true" type="Allgemein.Handlers.FileProtectionHandler, Allgemein" />
</httpHandlers>

<handlers>
      <add name="PDF" path="*.pdf" verb="*" type="Allgemein.Handlers.FileProtectionHandler, Allgemein" resourceType="Unspecified" />
</handlers>

My FileProtectionHandler.vb

Imports System
Imports System.Web
Imports System.Web.Security
Imports System.IO
Imports System.Web.SessionState

Namespace Allgemein.Handlers
    Public Class FileProtectionHandler : Implements IHttpHandler

        Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
            Get
                Return False
            End Get
        End Property

        Public Sub ProcessRequest(ByVal context As HttpContext)
            Select Case context.Request.HttpMethod
                Case "GET"

                    If Not context.User.Identity.IsAuthenticated Then
                        FormsAuthentication.RedirectToLoginPage()
                        Return
                    End If

                    Dim requestedFile As String = context.Server.MapPath(context.Request.FilePath)

                    If context.User.IsInRole("User") Then
                        SendContentTypeAndFile(context, requestedFile)
                    Else
                        context.Response.Redirect("~/Portal/Fehler403.aspx")
                    End If

                    Exit Select
            End Select
        End Sub

        Private Sub IHttpHandler_ProcessRequest(context As HttpContext) Implements IHttpHandler.ProcessRequest
            Throw New NotImplementedException()
        End Sub

        Private Function SendContentTypeAndFile(ByVal context As HttpContext, ByVal strFile As String) As HttpContext
            context.Response.ContentType = GetContentType(strFile)
            context.Response.TransmitFile(strFile)
            context.Response.[End]()
            Return context
        End Function

        Private Function GetContentType(ByVal filename As String) As String
            Dim res As String = Nothing
            Dim fileinfo As FileInfo = New FileInfo(filename)

            If fileinfo.Exists Then

                Select Case fileinfo.Extension.Remove(0, 1).ToLower()
                    Case "pdf"
                        res = "application/pdf"
                        Exit Select
                End Select

                Return res
            End If

            Return Nothing
        End Function

    End Class
End Namespace

After a joined effort with the OP it has been concluded that the MIR.Web.Allgemein is the root namespace.

In this case, the actual type name would be MIR.Web.Allgemein.Allgemein.Handlers.FileProtectionHandler which is the root namespace [dot] the actual namespace from code [dot] class name.