Over the course of messing with a new version of LINQ and other things, my WinFX Beta 2 install somehow got corrupted. When I tried to load the Workflow Foundation Designer I got the following error message:
Method 'ElementRemoved' in type 'TypeProviderHost' from assembly 'Microsoft.Workflow.VSDesigner, Version=18.104.22.168, Culture=neutral, PublicKeyToken=31bf3856ad364e35' does not have an implementation.
I tried removing everything (Visual Studio Extensions for WF, Orcas CTP, Windows SDK, WinFX Runtime) and reinstalling and the same thing happened. Finally I was able to find this which solved my problem, even though the original question is about Beta 1. Basically, if you have 2 versions of EnvDTE80 in the GAC, remove the one with the lower Version (right click->Properties->Version tab).
Now everything is working and I can get back to preparing for my upcoming Devcare presentation.