- I assumed that I was running the aD-patched version of AOLServer. I wasn't. (Grumble, gumble, former employees...)
- I somehow thought that .adp pages were working correctly, when they weren't.
I just spent a few hours with ngrep looking at HTTP headers. Once it became clear that modifying nsd.tcl wasn't having any effect, I decided to look at the version of AOLServer that I was running. Son of a gun, I wasn't running the version that I thought I was. I installed an aD version, and voila! Works like a champ.