I've upgraded Slackware 11.0 using the packages in today's Slackware security notices (and reinstalled ATI drivers so direct rendering would work) but have these messages from fc-cache during boot or manually executing:
"/usr/X11R6/lib/fonts/TTF": error scanning
"/usr/X11R6/lib/fonts/Type1": error scanning
"/usr/X11R6/lib/fonts/Speedo": error scanning
"/usr/X11R6/lib/fonts/cyrillic": error scanning
"/usr/X11R6/lib/fonts/misc": error scanning
And, being a typical user, "...but it's never done that before..." and that just happens to be true.
Odd that the font directories are actually in /usr/X11R6/lib/X11/fonts (/usr/X11R6/lib/fonts is a symbolic link) and ya have to wonder what it's yammering about -- and it only yammers about these, none of the others.
No clue, no clue.