According to thepost.ie Aer Lingus has prohibited usage of the iPod on all flights. They also prohibit use of devices that utilize a laser such as portable CD-Players and CD-ROM drives. I called the customer service line to verify this and it is in fact true. They claim that it has to do with the frequency with which the iPod operates and the fact that it uses LEDs.
Aer Lingus prohibits iPod usage on flights
“And if you want to de-stress after a tough working trip by listening to your new digital music player (eg, iPod), sorry: the Irish national airline has banned them. Again, it is out on its own on this one. The news will dismay long-haul passengers as the devices are popular in helping to while away airborne hours.”