Left system logged in overnight, in the morning the network icon had switched from an image of the jack to two computers, the upper right corner had switched from red power button to green running man, window title bars were gray, and every running program was suddenly using a different font (larger). This has happened twice in the past 3 months. I do normally leave myself logged in permanently, and don't do anything unusual with the theme, although I do run a program to switch the wallpaper every 10 minutes. Ubuntu 9.10.
ProblemType: Bug
Architecture: i386
Date: Wed Apr 21 07:45:22 2010
DistroRelease: Ubuntu 9.10
NonfreeKernelModules: nvidia
Package: gnome (not installed)
ProcEnviron:
LANGUAGE=en_US.ISO-8859-1
PATH=(custom, user)
LANG=en_US.ISO-8859-1
SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-21.59-generic
SourcePackage: meta-gnome2
Uname: Linux 2.6.31-21-generic i686
Forgot to mention, logout/login fixes it, a reboot is not required.