My "old" computer ran the 3D playback of a flight log just fine. My
"new" computer shows "No 3D graphics available"

I had the same problem on Seeyou version 2. Version 3 runs fine. Which
are you running.

I sent an e-mail to SeeYou and their response was to reduce the hardware
acceleration.

That seems to be their standard response and it does fix the problem,
but I don't think that crippling your hardware is the right answer. They
claim that it's not their problem. I think that they're wrong.

I did so and then the 3D graphics started working, but it
didn't seem like the performance was good.

It's not.

Tony V.