This seems odd when we are supposed to be able to teamwork with anyone from around the world.
I have just started 18 AUS and 18 INT at the same time using the same local WIBU key.
Both version are the original build 3006 and haven't been updated.
I started a third one (18 AUS build 4020) and they all seem to be running happily together.
I just don't have the latest hotfix (build 5100) installed - seems to be a few issues with it at the moment.
What builds are you running?
One of the forum moderators. Versions 6.5 to 25 Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10 Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10