I'm trying to find the Panasonic firmware for DVD-S52 (100E410) that has the updates for region free and no UOP/PUO.

I've looked all over the web, and all I find are references to:

dcevolution.net -- Apparently they had the firmware there for a while, but the site has changed and none of the links work.

xperience.podzone.net -- I've registered for the forums a couple of weeks ago, but the account has not been approved. I'm not sure if the site is still active.

firmwareupdate.us -- Has firmware for many models, but the DVD-S52 is not one of them.

Does anyone know of some other place where I can find the updated firmware? I'd be very grateful for any help.

Just because your model isn't listed on firmwareupdate.us doesn't mean it won't work. Another model might have the same controller.