Which version did you build and which folder did you copy it out of? Double check and make sure you got it out of Debug64 or Release64.
Ah ok, that was it. Thanks!
For anyone else who's trying to solve this: In Visual C++, right click on "Solution", Select "Properties", click on "Configuration Properties and select "x64" under "Platform". Then build and copy the plug-in from "samplecode/Output/Win/Release64/" (or ".../Debug64/") anywhere into Photoshop's plug-in folder. You needn't change the extension ".8bf" to capital letters. The filter "Dissolve" was accessible through "Filter -> Adobe SDK -> Dissolve..."