If you don't compile the interop sample for 64-bit and then try to use the x86 version in your 64-bit project, you'll get a BadImageFormatException when you try to compile your project. This is to be expected. However, we've noticed that the x64 configuration in the interop sample isn't correct, so when you specify x64, you get a x86 compilation anyway. You can change the configuration settings yourself in the configuration manager so that Windows7.SensorAndLocation build as x64 when the x64 configuration is chosen for Debug or Release. Note that XNA framework is x86 only, so you should uncheck the MarbleSample's Build check box in x64 configurations.
The team that posted the sample is working to update the download package. (Thanks to Yochay Kiriaty.)