Binary package hint: xserver-xorg
I updated two system from Hardy to Intrepid this week - October 21 and October 23. Both have nvidia cars in them. I followed the process I have in the past to change my /etc/apt.d/sources.list references from hardy to intrepid and hashed out any third party repositories. I then ran sudo aptitude update; sudo aptitude dist-upgrade.
Following the upgrade reboot X failed to start because no nvidia module was installed. I had to manually install the proper nvidia-glx-### (if I recall nvidia-glx-new did not work the first time). Following the install of the driver the Xserver would not run due to my old configuration still containing the RgbPath option. Once I commented this line out things were fine. Alternately, I could run dpkg-reconfigure xserver-xorg, but doing this and attempting to start X tried to load in the nv module which was not present on my system. I had to manually edit the xorg.conf file to resolve this.
Maybe, when install xserver-xorg or another related packaged, if there is an existing xorg.conf file that can be parsed to check for incompatibilities like RgbPath and hash out or remove the line.
this is the Intrepid RC release note
>nVidia "legacy" video support
The 71 and 96 series of proprietary nVidia drivers, as provided by the nvidia-glx-legacy and nvidia-glx packages in Ubuntu 8.04, are not compatible with the X.Org included in Ubuntu 8.10. Users with the nVidia TNT, TNT2, TNT Ultra, GeForce, GeForce2, GeForce3, and GeForce4 chipsets are affected and will be transitioned on upgrade to the free nv driver instead. This driver does not support 3D acceleration.
Users of other nVidia chipsets that are supported by the 173 or 177 driver series will be transitioned to the nvidia-glx-173 or nvidia-glx-177 package instead. However, unlike drivers 96 and 71, drivers 173 and 177 are only compatible with CPUs that support SSE (e.g. Intel Pentium III, AMD Athlon XP or higher). Systems with older CPUs will also be transitioned to the nv driver on upgrade.