Error Could not find type Microsoft.TeamFoundation.Build.Workflow.Activities in assembly 'Microsoft.TeamFoundation.Build.Workflow'

My next adventure is modifying my teams build template to allow us to do some custom post processing. We have it working in 2008 .proj files, but we want the symbols from the new 2010 template. I couldn't "compile" my workflow activities. pUnkOuter has the solution here. Thanks!