I am not sure what you are able to do on your system, could you try reapplying the 10.4.1 standalone updater? It may restore that file you quote which could have gotten corrupted. Also, you might boot in single user mode, Command-S at startup, and at the prompt, run the file system check, the command is a line or two above the prompt, starts with /sbin/ fsck.... in case the filesystem got itself fsckd up.