Part of the post build on my project is the execution of a program I wrote for testing the main application. Unfortunately, the post build process in visual studio locks up
This seems to be a known issue of VS 2010 (e.g. here and here) and it seems it won't be fixed that soon.
Regarding a possible workaround, similar to the one mentioned by @RichieHindle, one of the MS Connect persons suggests:
START /WAIT cmd /c YourPostBuildTool.exe