Good question.

The package is not installed and the question is therefore why not? If it is required in order for dkms to install the proprietary module (nvidia-current in this case), should it not be listed as a dependency of either dkms and/or the proprietary module package?

nvidia-current shows a dependency of "linux-headers-generic | linux-headers". There is no package in the repositories called "linux-headers" and "linux-headers-generic" was apparently not pulled in when I routinely installed nvidia-current.

This would appear to be the bug. linux-headers-generic needs to be made a dependency, although of which package I am not in position to specify.

bruce@Xenophon:~$ dpkg -l | grep linux-headers
ii  linux-headers-2.6.32-19                        2.6.32-19.28                                   Header files related to Linux kernel version 2.6.32
ii  linux-headers-2.6.32-19-generic                2.6.32-19.28                                   Linux kernel headers for version 2.6.32 on x86/x86_64
bruce@Xenophon:~$ dpkg -s nvidia-current
Package: nvidia-current
Status: install ok installed
Priority: optional
Section: restricted/misc
Installed-Size: 129560
Maintainer: Ubuntu Core Developers <email address hidden>
Architecture: amd64
Source: nvidia-graphics-drivers
Version: 195.36.15-0ubuntu1
Provides: xserver-xorg-video-6
Depends: x11-common (>= 1:7.0.0), make, sed (>> 3.0), dkms, linux-libc-dev, libc6-dev, linux-headers-generic | linux-headers, patch, acpid, libc6 (>= 2.3.2), libx11-6 (>= 0), libxext6 (>= 0), zlib1g (>= 1:1.1.4)
Recommends: nvidia-settings
Conffiles:
 /etc/OpenCL/vendors/nvidia.icd 3ab6fef7906dfd11f3d931ddffe812f4
Description: NVIDIA binary Xorg driver, kernel module and VDPAU library
 The binary driver provide optimized hardware acceleration of OpenGL
 applications via a direct-rendering X Server. AGP, PCIe, SLI, TV-out
 and flat panel displays are also supported.
 .
 This package also includes the source for building the kernel module
 required by the Xorg driver, and provides NVIDIA's implementation of
 the Video Decode and presentation API. The latter enables acceleration
 for NVIDIA 8 and later series cards for h264 video.
 .
 GPUs such as GeForce series 6 or newer are supported.
 .
 See /usr/share/doc/nvidia-current/README.txt.gz for a complete list
 of supported GPUs and PCIIDs
bruce@Xenophon:~$ apt-cache search ^linux-headers
linux-headers-2.6.32-19 - Header files related to Linux kernel version 2.6.32
linux-headers-2.6.32-19-generic - Linux kernel headers for version 2.6.32 on x86/x86_64
linux-headers-2.6.32-19-preempt - Linux kernel headers for version 2.6.32 on x86_64
linux-headers-2.6.32-19-server - Linux kernel headers for version 2.6.32 on x86_64
linux-headers-2.6.32-304 - Header files related to Linux kernel version 2.6.32
linux-headers-2.6.32-304-ec2 - Linux kernel headers for version 2.6.32 on x86/x86_64
linux-headers-ec2 - Linux kernel headers for ec2 machines
linux-headers-generic - Generic Linux kernel headers
linux-headers-lbm-2.6.32-19-generic - Header files related to linux-backports-modules version 2.6.32
linux-headers-lbm-2.6.32-19-server - Header files related to linux-backports-modules version 2.6.32
linux-headers-server - Linux kernel headers on Server Equipment.
linux-headers-virtual - Linux kernel headers for virtual machines
linux-headers-2.6.31-10-rt - Linux kernel headers for version 2.6.31 on Ingo Molnar's full real time preemption patch
linux-headers-lbm-2.6.32-19-preempt - Header files related to linux-backports-modules version 2.6.32
linux-headers-preempt - Linux kernel headers for Low Latency Servers.
linux-headers-rt - Realtime (RT) Linux kernel headers
bruce@Xenophon:~$