Can't view TASK MANAGER ?

You might be having problem with your computer's poor performance recently , the main reason in that your anti virus protection is not so efficient or the pen drive that you inserted had malicious viruses that are strong enough to break your firewall and attack the computer and its performance. One of the majorly affected point because of this problem is the Invisible TASK MANAGER, you really can't access it, try an updated anti virus full PC scan, else just format the drive with new pack of OS.