Just tested with user. As it turns out, you nailed it, JCL! (Thank God.) The problem was the DEP setting.

Now the only question remaining is about the dev vs. public versions. Here's exactly what's in the game install (and what's causing the problem with DEP):

{app name}.exe (automatically created during Publish based on acknex.exe)
acknex.dll
d3dx9_30.dll
acknex.wdf
{app name}.wdl (used to launch game with other wdls in wrs files)

That's it. The rest of the installation includes various wrs files with wdls and graphics/sound resources, a third-party dll used to change the app icon after the game engine starts, and some raw media files (ico, pcx, tga, wmv).

Again, all of the above files come straight out of the output .cd folder after using Publish.

Is it possible the icon-changing dll is the culprit? If not, you may want to check into this, since it would mean that non-dev files are resulting in the DEP problem.

Many thanks, JCL, for pinpointing this one so quickly.