your lsws is running as nobody. so the cache files are supposed to be owned by nobody:nobody. is the one owned by root generated at a different time or the name looks different from the rest?
run 'top' from command line and see if your server has higher i/o wait when site is slow (before you clear the cache files). if so, you want to purge your cache more often or move your cache folder to shm as suggested earlier.