I have relocated to a new machine (Win7Pro-32bit, VS2008, IVF 2011.4.196). Everything installed perfectly, my .vfproj loads, shows all files and components, but the "compile" button is now greyed, none of the source files can be compiled, even though they are definitely included in the build. Evidently some project or global setting has been changed -- suggestions appreciated.
Added comment: amazing how posting here can catalyze a solution. Turns out the file extension registrations within the IVF integration had vanished, pressed reset and all is well.