The UK is mostly PAL, and the U.S. is ATSC.
PAL uses a 50hz signal.
ATSC uses a 60hz signal.
It's not a firmware issue, I wouldn't think. It's more likely an issue that one player isn't designed to work in a different region.
I recently brought a BD-C6900 blu ray player back from the US to the UK. It will not load any discs, I've tried Region A and multi region Blu rays also dvds and cds. Is this a firmware problem (Ive updated it to the latest version) or is it just a case of the player not working when attached to a UK TV. I'd be grateful for any help.