Adding/Removing/Resetting Users

Hello, I'm having issue adding/removing users from the system. I have a user in the system that I'm trying to replace because I've forgotten his pass. When I go to add a new user to the system I often get this error: \"Missing file. Possible Module \"users\" missing!\" (I have double checked and this user is not attached to any project or company if that helps.) When I try to delete a current user, there is not delete button. (At least that I can see) And when I try to reset the password of a current user. The new password I'm sent via email for that will not work to login. System: My system says \"Your system is the latest version available.\" I'm not sure what version it is though. I'm running this on a shared server. Dual Xeon E5520 2.26 GHz Quad Core Processors. CentOS 5.5 Enterprise Linux x86. 12 GB of DDR2 or DDR3 RAM. I hope that helps. Looking forward to any help you guys can provide!