My server wont let me use Commands

Hiya, my commands are not working on my server. I've reset the Op's, Changed the software for Bukkit, deleted mods but it still isn't working.

It shows this error message whenever i try to type in any commands like /fly (player), creativemode (player) "Unknown or incomplete command, see below for error at position 1: /<--[HERE]"

It was previously working but am confused as to why it is not now

Yes! Tried both those methods and is still not working

It says that (player) is op, I've tried taking the players on and off both ways but it still isn't working.