Hmm... I thought the model looked a little odd. After I added rotation, I found it looked 2D, as it it had been flattened onto a plane. After about 2 hours of investigation (an hour on the train and this hour for lunch), I came across this little gem of code:

I think I need to take a break...

Also, for anyone who has the Quake II source code handy - how does it decide where the base of a model is? The Gladiator model has a base of around -25.0f on Y, but I suspect that's arbitrary. I'll check the source when I get home (I have it on my main PC).