Using the || operator makes the operator< invalid, because the following is true:

("foo", "bar") < ("bar", "foo")    < is true for second string
("bar", "foo") < ("foo", "bar")    < is true for first string
We fix this by fully comparing one string, then trying the other one.

stepmania/src/CourseUtil.h

@@ -45,7 +45,9 @@ public:
 	const RString &GetPath() const { return sPath; }
 	bool operator<( const CourseID &other ) const
 	{
-		return sPath < other.sPath || sFullTitle < other.sFullTitle;
+		if (sPath != other.sPath)
+			return sPath < other.sPath;
+		return sFullTitle < other.sFullTitle;
 	}
 
 	XNode* CreateNode() const;