new Dapper install - X problems

[William Chapman]

Just installed Dapper - upgraded Breezy system that has been working well.
X fails to start - get the following "X server output":

(==)Log file: "/var/log/Xorg.0.log", Time: ...blah...
(==) Using config file: "/etc/X11/xorg.conf"
dlopen: /usr/lib/xorg/modules/extensions/libGLcore.so: undefined
symbol: __glXLastContext
(EE) Failed to load /usr/lib/xord/modules/extensions/libGLcore.so
(EE) Failed to load module "GLcore" (loader failed, 7)
(EE) Failed to load module "nvidia" (module does not exist, 0)
(EE) No drivers available.
Fatal server error:
no screens found

The nvidia driver always worked flawlessly with Breezy, and Hoary.

The web has a number of similar, recent (early '06) complaints
relating to Debian-Unstable, but nothing really definitive (at least
to me).

The /etc/X11/xorg.conf is totally vanilla from the Ubuntu installer; I
have never touched it.

The "detailed X server output" doesn't seen too interesting.  There
are a few font directories that don't exist.

Interestingly, perhaps, is that these missing FontPaths immediately
preceed the Section "Module" block in xorg.conf that begins with Load
"GLcore" (which fails to load) as the first command.

Any hints would be appreciated.

William J. Chapman