Just noticed today that my visual studio crashes when I try and go into design mode.

I'm not honestly sure what causes this problem as I dont use this VM very often however i think its linked to either Office 2007 or Visual Studio 2008 SP1.

as a fix I manually removed the Visual Studio 2008 Web Authoring Component and then re-added from my Visual Studio CD

you can find the exe file within then WCU\WebDesignerCore\ folder

This fixed the problem for me hopefully it will for you also.