Do you have latest drivers from nvidia.com installed ?
No, it has the drivers that worked well with the TV & DVD player, which is not the latest - it's an HTPC 1st after all - as the latest drivers had a glitch when coming out of hibernation.

I understand that on your other system with GeForce, framerate was good ?
Other system has 6800XT with 256MB and 2GB of main RAM, so it's a bit above average specs
The HTPC has a 6100, which is an integrated graphics chipset.

For OpenAL, I personnally am able to fix and find it, but for players and users at large, that may be a tougher proposition (though even personnally, not tracking OpenAL closely means I've no idea if the software OpenAL DLL I found was really a recent one, if you provided one, you would be able to make sure it worked well for all your game's needs).

Most of the "Loading ..." overhead is related to pushing things into OpenGL display lists, see my posts in "Stage 5 feedback" thread.
Ok. As other have pointed, you usually use display lists only for static geometry. For animated geometry, vertices and normals are usually interpolated on the fly and rendered directly, which allows to have many animation frames, skeletal animations, merged animations, etc. even on high polycount models without facing a huge memory consumption.
Display lists are also unlikely to perform very well when used in that fashion, nVidia drivers may not balk too much, but chances are your framerate is lower than what it could be.

Can you reproduce this ? By "at startup" do you mean that it occured right after running the game (not e.g. at the loading of "New Game") ?
Didn't happen again, and when it happened, I had just closed an instance and restarted another, so I'm unsure wether it was an error due to the previous instance not being completely terminated, or to the new instance that was just starting up.