I've never used FileCache, but from the OP's question it looks like it's a directory. If it is, you almost certainly want mode 0700, not 0600. Only giving read and write, but not execute, makes it impossible to use anything in that directory:

$ mkdir t100
$ chmod 600 t100
$ ls -ld t100
drw-------    2 sgifford sgifford     1024 Jul 22 13:41 t100
$ cd t100
bash: cd: t100: Permission denied
echo 'hi' >t100/test
bash: t100/test: Permission denied
$ cat t100/test
cat: t100/test: Permission denied