I was using the firewire hub which the Apple Cinema Display provides for connecting my ipod mini. This worked perfectly with Tiger: iTunes opened each time I connected the iPod to the cable, and it also charged it as expected. But once I upgraded to Leopard this wasn't working anymore; the iPod was charged but iTunes didn't show up for synchronizing, basically because the iPod didn't mount at all.
It did synchronize if I used the USB cable, but that is very inconvenient for me since all the USB ports are in use already and I don't like to be plugging and unplugging cables constantly.
But today I found the solution (or more exactly work-around): to connect the ipod, using the Firewire cable, directly to the computer, instead of using the Display's hub.
I don't know what is the reason for this change/bug, unless they definitely want to eradicate Firewire iPod interfaces from the market or something. Luckily I don't have any other Firewire device, or I'd be screwed!