The french version of Atlantica Online works almost perfectly,
the graphics aren't that slow and the onlys bug remain are that sometimes it become impossible to clic on a monster (and that's problematic when it comes to battle...), and that some part of the maps make the game very laggy (desert background, training center background, ...).
The version i used to test it was CrossOver Games MAC 9.0.0 and i saw no problem in the installation.
As the french client doesn't have any problem during the login, maybe it could help to discover why it bug in english version.