It sounds to me like you might have a format error in your attempts to use SUDO RM - RF from the Terminal command line.
...just to clarify the terminal command for removing a file permanently while using ROOT permissions temporarily (as SUDO):
to get the file auto inserted behind the command you need to type the following -
sudo rm -rf
(if you drag your cursor over the above command you will note that there is ONE space between the "rm" and the "-rf" followed by another SINGLE space...)
when you are in the Terminal this will leave your text entry cursor at the exact spot that the path to your file in question needs to be entered in order to complete the command.
NOW is when you use the Finder to drag and drop the file in question onto the Terminal window where it will write the rest of your command and complete it with proper syntax and format.
When you hit return, you will be prompted to enter your admin password (which will NOT display as you type it), then hit return again.....that file should now be gone.
(If you enter an additional sudo command before the internal timer releases your password, the Terminal will execute it without requesting you to type your admin password a second time.....once the internal timer expires, you will be prompted for your password again.)
