Well , if you want to burn different compilations then you are forced to set two jobs, however in your case you are right. Maybe you should take in mind the reply of DavidW. Try another serial number for your Nero(If you can find one ) to have full functionality.
Something else. Maybe Nero 6 doesnt support simultaneous burning as you want it. Why dont you install the Nero version that works with the other machines? If it doesnt recognize your drives, then ... you will have to wait for an update of Nero 6.
I ll check on my machin with Nero 220.127.116.11 ultra and tell you if i have the same problem.