I have a few computers that are running XP SP3 that will not allow the Task Manager to open. I have done a lot of Google Searches on this issue, and a lot of people start talking about how you probably have Spyware or a Trojan or some type of Virus. One of these PC's I can almost guarantee does not have anything malicious on it as its still a fresh install.
So then I tried opening taskmgr.exe from System32 and no dice, however if I do a Run As using Administrator it opens right up. The user accounts have local Administrator rights, and this is happening on my own PC as well, and I have Local and Network Admin rights.
I also tried to add myself in the security tab under properties for taskmgr.exe, that did not work either.