'xscreensaver -lock-mode' will pop up a dialog box that says
"ERROR: RESOURCES NOT INSTALLED CORRECTLY" wherever text
would normally appear. The colors are missing as well.
Works OK here on a base 5.2 install.
You might try moving /usr/X11R6/lib/X11/app-defaults/XScreenSaver
out of the way to see if it's causing problems, or deleting
your ~/.xscreensaver file.