Releasing a fix right now.
The handling of Northern Ireland is a bit odd, and has caused us a lot of troubles. I don't really understand why our code did like it did now though. It's most likely that someone has pointed something out that did not comply with Geocaching.com, and that we didn't really do the research and just trusted the user.
I hope our current fix is correct. According to Geocaching.com, Northern Ireland is a part of United Kingdom. We faked the logged areas of a user and added only United Kingdom. Our new maps then made UK and Northern Ireland green in the world and Europe map. Then we changed it to be only Ireland, and then Ireland (except Northern) was made green. This seems like the correct behaviour.
Due to external data-caching it might take up to 10 days before this takes effect.