c# calling managed c++ dll doesn't run in ide

I'm in VS2012, win7. When I press the green arrow to run the c# app in debug which references my managed c++ dll (the compiler is perfectly happy), I get 'unrecognized error occurred in the windows web services framework. If I do ctrl-f5 (start without debug) it doesn't give me the error, but the hourglass circle spins a bit and vanishes. Very stuck I am.

thanks,

sb