re-build existing 32 bit app to 64 bit

I have an exiting application. It is a vb.net program that dynamically calls a c++ dll. Everything works great as 32 bit. The goal of the project is to build it as a 64 bit application; both the vb.net and the c++ dll program. Sounds easy enough but I've been pulling out hair trying to get it working. If you can re-build the app as a 64 bit app that has no runtime issues, that's the project. ## Deliverables Please document what you did to make it work in 64 bit. This is important. I will, of course, supply you the entire project and dev files. I'm using MSVS 2010. If you don't have access to 2010, I can pull in a backup of the project as vs2008.