Note that I am attempting to answer this question having not looked at the WPILib in several years...
The error you are describing sounds like you are trying to instantiate an interface rather than a fully implemented class. Posting a code snipit might help diagnose the exact problem. Do you have a line in your code like:
Code:
SpeedController sc = new SpeedController();
or
Code:
SpeedController sc = new IVictorSP();
If so, try replacing it with something like:
Code:
SpeedController sc = new VictorSP();
Basically what seems to be happening is that there exists a class "SpeedController" that has a method "Set" that is not implemented (it is pure virtual), making this class be an interface. Other classes, such as Victor, Tallon, etc, will derive from the SpeedController class and must implement the Set() method. The error you are reporting makes it sound like you are trying to instantiate one of the parent classes/interfaces, rather than the child class that actually has the implementation.
Check your documentation and make sure you are instantiating the correct class.