After writing some more test programs, I've determined that the beagleboard's GLES2 and SDL don't play nicely together. The good news is now I know.
The bad news is that the dexter code base is tightly coupled to SDL. I've wanted to decouple this before but it has always been too much work to justify my efforts. Well, I think I will finally have to break down to do it. The resulting decouplage (is that a word?) will be an improvement but who knows how long it will take me to do. I will probably write a generic set of structs/classes that have the same structure as the SDL_Surface struct so I can just do a find/replace and keep most of the code the same.