You might want to disable all of Quicktime through the Extensions Manager and then install 4.1.2 again. To do this, open the EM, set it to View as Packages, and then turn all of the Quicktime packages off. Restart, and see if the message goes away. If it does, install Quicktime 4.1.2 again-- if it doesn't, look through your extensions folder for anything called Quicktime and disable it, then install 4.1.2 again.