it's true you have the newest firmware but if it's asking to update I would highly recommend not doing it because it could change some stuff and brick your wii. I would recommend patching the iso file and reburning it. Running an unpatched game is something I will not do if it's not my region.
I currently have two imports
Guilty Gear XX
Donkey Kong Taru Jet Race
Play great with patch and regionfrii