the tv automatically updates during standby mode when not being used. mine did the same thing, I actually thought it was weird it was available for download. I was just checking these forums which is when I even heard about this new update went to check and mine was already updated, I use Ethernet straight to the tv.
I turned my automatic updating off. I now have to find a usb key that is under 2 gigs. I'll try and install the update that way seeing customer support and Panasonic keeps saying to reset the entire tv. Problem is that doesn't reset the firmware version.