From the instructions page:
With unit powered down (not in stand-by), press and hold the 'Play' and 'Open/Close' buttons while powering up the unit. With the 'Menu' button on the remote you can scroll through data that pertains to your unit. With each button press, another data identifier is shown on the front panel display. Press until you see 'ESS-xxxx', if the number is lower than 6334-6, you should download the firmware. If higher, -7 or -8, do not proceed with this update as your unit is the most up to date available. The version numbers -7 and -8 include all current fixes and also the IEEE-1394 fix (which is available for those with lower version numbers, it is a hardware and firmware fix, so you will have to call our service department to arrange)
