Sorry, I misunderstood.
There are 2 cards:
00:0a.0 VGA compatible controller: nVidia Corporation NV18 [GeForce4 MX 440 AGP 8x] (rev a2)
01:00.0 VGA compatible controller: nVidia Corporation NV18 [GeForce4 MX 4000 AGP 8x] (rev c1)
I use 1 PC and 2 videocards/monitors/keyboards/mice
The driver is nvidia's legacy 96.43.01
But as I said in the OP above: I can run Trem just fine with that driver but the Debian libraries from last summer.
So I do think that the problem is mine that I upgraded only xserver-xorg-core + xserver-xorg. Except upgrading everything is a 2 day process because I am on a dialup modem.
PS I didn't mean to imply errors on the part of trem. in killing X, just the fact that "X gets killed for whatever reason when starting Trem."