I'm running Vista Business and am logged in as Administrator. I can't seem to message a logged in user via Task Manager. It says that I don't have permissions for this. I've tried setting it up in a few different accounts but I can't get it to function correctly. Am I missing something?

Yes, easy mistake to make. All you need to do it right click Task Manager, select Properties, then select the Advanced button. In here you will need to select "Run as Administrator. It should work fine after that.