Exchange 2010 SP2 Update error on SBS 2011

hello,

I installed Exchange 2010 sp2 on a Windows sbs 2011 (german). Everything looks fine. But until the Cient Access Role Update, the Setup crashes, the error Messages is too long, to display on the Setup window, so the hole Setup crahes. In the error log, the following error is displayed:

[12.18.2012 21:08:06.0394] [1] The following 65 error(s) occurred during task execution:
[12.18.2012 21:08:06.0394] [1] 0.  ErrorRecord: Der Typ [Microsoft.Web.Administration.ServerManager] kann nicht gefunden werden. Stellen Sie sicher, dass die Assembly, die diesen Typ enthält, geladen wird.
[12.18.2012 21:08:06.0394] [1] 0.  ErrorRecord: System.Management.Automation.PSArgumentException: Der Typ [Microsoft.Web.Administration.ServerManager] kann nicht gefunden werden. Stellen Sie sicher, dass die Assembly, die diesen Typ enthält, geladen wird.
   bei System.Management.Automation.MshCommandRuntime.ThrowTerminatingError(ErrorRecord errorRecord)
[12.18.2012 21:08:06.0394] [1] [ERROR] The following error was generated when "$error.Clear(); 
          function SetConfigurationSectionAttribute([System.String]$sectionPath, [System.String]$locationPath, [System.String]$attributeName, [System.Object]$value)
          {
            $serverManager = New-Object Microsoft.Web.Administration.ServerManager;
            $configuration = $serverManager.GetApplicationHostConfiguration();
            $configurationSection = $configuration.GetSection($sectionPath, $locationPath);
            $configurationSection.GetAttribute($attributeName).Value = $value;
            $serverManager.CommitChanges();
          }

The server looks fine, Mailbox and owa are available

get-exchangeserver Show 14.2 (Build 247.5) as Version number. Is the sp 2 installed successfully?