No, I'm not going to talk about Instructors having conflicts with students or each other. Instead, I'm here to talk about scheduling conflicts and how you can prevent them.

One thing that has been in the system for a long time but has probably been forgotten, is a preference to Check Instructor Schedule Conflict. This preference is located on the Faculty tab in the section for Assigning an Instructor to a Course. It is a user-specific preference, but I would think everyone in your institution should have it enabled. The only time I would think you would want it off is if you have a lot of courses where you assign the same second teacher as a supervisor or sub. Really though, this preference just warns you of the conflicts and does not enforce you to not assign the instructor if they are already teaching a course. I don't know about you, but I can't be in two places at the same time, and we probably shouldn't expect our instructors to be.

Something new in the August release of Manager (8.0.090) was a function to report conflicts. The function is named INSTCONF, and a description of it is available here. The idea is that you could put this on an instructor report of courses to list the conflicts. An example report can be downloaded from here (import instructions located here), and run from Reports -> Faculty -> Instructor Lists. It looks like this (conflicts highlighted):

Hopefully, you are now well armed to prevents such things!