I have the same problem with fc-cache on my amd64 which is cleanly installed from etch. I do not have the problem on my i386 machine which recently had everything font related reinstalled. The fonts.conf file are identical on the two machines.
There seems to be fonts generated in the cache directory, so my suspicion is that fc-cache does the right thing but returns with an error code for some reason, connected to the machine being 64 bit. If you don't have an amd64 environment to test on, I can offer temporary access to the machine. It is currently not doing anything important. Jacob Hallén
