I've got this error while upgrading to 5.5 :

Upgrading DotNetNuke
Current Assembly Version: 05.05.00
Current Database Version: 05.04.04

Upgrade Status Report

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Server Error in '/' Application.
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An item with the same key has already been added.
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.ArgumentException: An item with the same key has already been added.

Source Error:

The source code that generated this unhandled exception can only be shown when compiled in debug mode. To enable this, please follow one of the below steps, then request the URL:

1. Add a "Debug=true" directive at the top of the file that generated the error. Example:

  <%@ Page Language="C#" Debug="true" %>

or:

2) Add the following section to the configuration file of your application:

<configuration>
   <system.web>
       <compilation debug="true"/>
   </system.web>
</configuration>

Note that this second technique will cause all files within a given application to be compiled in debug mode. The first technique will cause only that particular file to be compiled in debug mode.

Important: Running applications in debug mode does incur a memory/performance overhead. You should make sure that an application has debugging disabled before deploying into production scenario. 

Stack Trace:

[ArgumentException: An item with the same key has already been added.]
   System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) +51
   System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) +7462172
   System.Collections.ObjectModel.KeyedCollection`2.AddKey(TKey key, TItem item) +93
   System.Collections.ObjectModel.KeyedCollection`2.InsertItem(Int32 index, TItem item) +38
   System.Collections.ObjectModel.Collection`1.Add(T item) +117
   DotNetNuke.ComponentModel.SimpleContainer.AddBuilder(Type contractType, IComponentBuilder builder) +111
   DotNetNuke.ComponentModel.SimpleContainer.RegisterComponentInstance(String name, Type contractType, Object instance) +121
   DotNetNuke.ComponentModel.AbstractContainer.RegisterComponentInstance(Object instance) +82
   DotNetNuke.ComponentModel.ComponentFactory.RegisterComponentInstance(Object instance) +77
   DotNetNuke.ComponentModel.ComponentBase`2.get_Instance() +166
   DotNetNuke.Entities.Host.Host.get_SchedulerMode() +19
   DotNetNuke.Services.Scheduling.SchedulingProvider.get_SchedulerMode() +5
   DotNetNuke.Services.Scheduling.DNNScheduling.CoreScheduler.Halt(String SourceOfHalt) +13
   DotNetNuke.Services.Scheduling.DNNScheduling.DNNScheduler.Halt(String SourceOfHalt) +47
   DotNetNuke.Services.Install.Install.UpgradeApplication() +924
   DotNetNuke.Services.Install.Install.Page_Load(Object sender, EventArgs e) +272
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +50
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627

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Version Information: Microsoft .NET Framework Version:2.0.50727.3603; ASP.NET Version:2.0.50727.3614


Thank you to help me.