(Tentative documentation of the Rhea concept Uniqueness of Pages)
Note: A page's name needs to be unique to all sections of all classes.
The best way to make a page which is specific to your class (like to discuss homework) have a unique name is to add the class name/professor/semester at the beginning (or end). There may be a way to automate this in the future, but right now, just copy and paste.
For example: [[MA 375 Spring 2009 Walther Homework 1 Problem 4|Problem 4]]. Copy and paste that, so if you want to talk about problem 37 of homework 3, it's as simple as replacing 1 with 3 and 4 with 37: [[MA 375 Spring 2009 Walther Homework 3 Problem 37|Problem 37]].
If the page relates to all classes (for example, a definition of Matrix) then add the general class category. (For example [[Category:MA375]])