I did some Googling and came up with a solution.
- Remove GTK-Qt Theme Engine and GTK Theme Switch. If you're using GNOME, you probably don't need these packages.
sudo apt-get autoremove gtk-qt-engine gtk-theme-switch
- Get rid of your gtkrc-2.0 file. You could rename it or just blow it away, depending on how confident you are that you won't need it again.
mv ~/.gtkrc-2.0 ~/.gtkrc-2.0.bad