Recently we had an issue with VS2008 freezing (stuck, not responding... you name it...) when you try to switch to design-view of a web page (aspx).
Since we merely changed the markup lately, it's been quite annoying.
This issue was very time consuming as the web offered no solution for this behavior (the solutions offered weren't helpful - at least for our case).
Having a tight deadline in our project, we really had to solve this issue quickly and decided to use brute-force by tearing the Master Page (which seemed to be causing this) apart for finding the problematic markup.
I repeatedly removed blocks of markup and tried to switch to design-view after each block was removed.
Most of the time switching to design-view caused the devenv.exe (VS2008) to stop responding and I had to kill the process (via the Task Manager).
After a while, I have found the markup that was preventing me from switching to design-view.
For what it's worth, the markup is presented here: (Very weird, can't see why this should be problematic).
<asp:Label ID="lblOrganisation" CssClass="changeOrganization" runat="server" Font-Names="Arial"
Height ="23px" Text="Switch Organization:" meta:resourcekey="lblOrganisationResource1">
Shall you have another solution or an explanation why Height="23px" (the block that I removed) should cause this, please leave a comment.