Editing ASPX in Visual Studio 2010

I have recently upgraded from Visual Studio 2005 to Visual Studio 2010 (and also moved from Windows XP 32 bit to Windows 7 64 bit).

Whenever I edit an ASPX file in my project VS20开发者_如何学Go10 throws an exception:

"A first chance exception of type 'System.InvalidOperationException' occurred in System.Web.dll
Additional information: Operation is not valid due to the current state of the object."

I have edit and continue turned on and am targeting X86 (as 64 bit E&C doesn't work)

Is there a known issue for this or is it something I'm doing wrong?