I re-installed 10.04 on a different disk, and found that a fresh install used the nouveau driver as well and that it too exhibited the screen garbage problem.  However, with 10.04, selecting "hardware drivers" offers the Nvidia accelerated graphics driver (version 96), which, once activated, works correctly with no garbage.

So, the following driver works OK:

johnn@johnn-laptop:~$ lsmod | grep -i nv
nvidia               4701243  32 
agpgart                31724  2 nvidia,intel_agp
johnn@johnn-laptop:~$ 
johnn@johnn-laptop:~$ dpkg --get-selections | grep -i nvidia
nvidia-173-modaliases				install
nvidia-96					install
nvidia-96-modaliases				install
nvidia-common					install
nvidia-current-modaliases			install
nvidia-settings					install
johnn@johnn-laptop:~$ dpkg --status nvidia-96
Package: nvidia-96
Status: install ok installed
Priority: optional
Section: restricted/misc
Installed-Size: 21868
Maintainer: Ubuntu Core Developers <email address hidden>
Architecture: i386
Source: nvidia-graphics-drivers-96
Version: 96.43.17-0ubuntu1
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 (>= 2.1), libx11-6 (>= 0), libxext6 (>= 0)
Recommends: nvidia-settings
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.
 .
 GPUs ranging from GeForce series 2 (except for GeForce2 GTS/GeForce2 Pro,
 GeForce2 Ti and GeForce2 Ultra) to Geforce series 7 are supported.
 .
 See /usr/share/doc/nvidia-96/README.txt.gz for a complete list
 of supported GPUs and PCIIDs
johnn@johnn-laptop:~$ 

And the following drivers DO NOT work correctly on this hardware:

johnn@johnn-laptop:~$ dpkg --get-selections | grep -i nouv
libdrm-nouveau1					install
xserver-xorg-video-nouveau			install
johnn@johnn-laptop:~$ dpkg --status xserver-xorg-video-nouveau 
Package: xserver-xorg-video-nouveau
Status: install ok installed
Priority: optional
Section: x11
Installed-Size: 272
Maintainer: Ubuntu MOTU Developers <email address hidden>
Architecture: i386
Version: 1:0.0.15+git20100219+9b4118d-0ubuntu5
Replaces: xserver-xorg (<< 6.8.2-35)
Provides: xserver-xorg-video-6
Depends: libc6 (>= 2.4), libdrm-nouveau1 (>= 2.4.16), xserver-xorg-core (>= 2:1.6.99.900)
Description: X.Org X server -- Nouveau display driver (experimental)
 This driver for the X.Org X server (see xserver-xorg for a further description)
 provides support for NVIDIA Riva, TNT, GeForce, and Quadro cards.
 .
 Although the nouveau project aims to provide full 3D support it is not yet
 complete, and these packages do not include any 3D support.
 Users requiring 3D support should use the non-free "nvidia" driver.
 .
 This package is built from the FreeDesktop.org xf86-video-nouveau driver.
Homepage: http://nouveau.freedesktop.org/wiki/
Original-Maintainer: Debian X Strike Force <email address hidden>
johnn@johnn-laptop:~$  
johnn@johnn-laptop:~$ dpkg --status libdrm-nouveau1
Package: libdrm-nouveau1
Status: install ok installed
Priority: optional
Section: libs
Installed-Size: 452
Maintainer: Ubuntu X-SWAT <email address hidden>
Architecture: i386
Source: libdrm
Version: 2.4.18-1ubuntu3
Depends: libc6 (>= 2.3.4), libdrm2 (>= 2.4.3)
Description: Userspace interface to nouveau-specific kernel DRM services -- runtime
 This library implements the userspace interface to the nouveau-specific kernel
 DRM services. DRM stands for "Direct Rendering Manager", which is the
 kernelspace portion of the "Direct Rendering Infrastructure" (DRI). The DRI is
 currently used on Linux to provide hardware-accelerated OpenGL drivers.
Original-Maintainer: Debian X Strike Force <email address hidden>
johnn@johnn-laptop:~$