I would imagine that itunes has its own built in engine to support cd writing and this is whats causing the problem with nero.
Now Ive never used itunes so i cant direct you on how to turn it off or even if you can, but a good place to start would be in the settings or options pages of itunes. Hopefully you can disable there cd writing facility.
As far as ipod / itunes goes this is my main issue with it, there is a winamp plugin apparently to get that to work with your ipod but again not having any experience with one cant really help much more than that you can find the plugin here click here
Hopefully someone who knows a bit more about itunes will be about and can point you in the right direction.