I figured out the problem. There was one project option that seemed to cause it to suddenly work. Your ListAdapters program uses a Multi-Byte character set whereas the c++ Visual Studio 2005 default character set is unicode. I bet this was causing a problem with OpenFilterDriver because the default string being passed didn’t hook up with the driver properly (you could probably shed more light on the exact reason why).
Anyhow, I think we’re in business now – thank you!