Due to a programming style I started when I learned Java (which doesn't apply to C++), I tried to delete the OpenGL texture when any class instance was destroyed, which meant that any copy that was destroyed would remove the texture (and since I was returning an instance, it actually made a local copy and returned a second copy, then destroyed the first one, which meant that no texture actually made it through).

I've since stopped deleting textures on my own and now let the OS deal with it when I'm done, and textures now work perfectly.
(now the only trick is generating them properly)