Oggi ho ricevuto la notifica con la soluzione al bug che ho inserito su Microsoft Connect relativamente all'errore descritto in questo post: Visual Studio 2008 issue: problemi di renderizzazione a design-time. La soluzione indicata è la seguente:

Hi Knodev, The absence of "ViewRendering.get_Visible()" is a telltale sign that your System.Web.dll framework version is incorrect. This could be the result of an incorrect Windows Update patch. You will need to go to Windows\Microsoft.NET\Framework\v2.0.xxxx, right click on System.Web.dll and theck version number. It should be 2.0.50727.13xx or higher. If it is lower that 1300, you will need to uninstall the 3.5 and 2.0 and reinstall. Thanks! Jeff
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Per visionare tutta l'History del problema potete visitare il seguente link: Visual Studio 2008 Team Suite issue with ASP.NET designer.