I had not tested OpenVRML‘s Mozilla plug-in for some time, during which I’d made a number of nontrivial changes to the library. So when I went back to it a couple of weeks ago, I was not exactly shocked that it didn’t work at all. But when I finally realized what was causing the deadlock, it was one of those “How did this ever work?” moments.
So the plug-in has been restored to basically working condition. It still needs a bit more surgery before it will shut down gracefully. Right now it’s hacked by sending SIGTERM from the Web browser process. I also have no faith that its URI fetching is actually working.