Taskmngr will not function

I can use all other functions of ctrl alt & del individually but nothing happens when i try to open the task manager. I have also tried to open it via the taskbar but nothing (not even a flicker), i have run several anti virus products that have not detected anything. Is there a setting in the registry i can try?
I have already tried under hkcu software/microsoft/policies but cannot see anything and no session folder exist under that….help