Either shift or option + eject (can't remember which) opens it. If you keyboard doesn't have eject, press and hold F12. If you have parallels installed and running, make sure it hasn't given your optical drive to Windows; if so, you'll have to transfer it back to the mac through the Parallels menu before you can use it on the mac side.
Oh, also, I've seen some revews of the Logitec cordless KBs that they have issues if the wireless dongle is plugged in after the system boots sending some of the keys correctly, such as the extended function keys and the command keys.