Thank you for providing the example of the issue. Since I am unfamiliar with Swedish operating systems and the alphabet itself, I have some questions.
In the english FileMaker, the Manage / Database / Fields panel has a drop down in the upper right for "view by". By default, this sets to the "creation order" of the fields, and needs to be changed to "field name" in order to alphabetize the fields. Does "i bokstavsordning" mean "field name"?
Is your installation of Mac OS X localized for Swedish? Do other applications on the Mac sort as expected? Can you test FileMaker Pro 11 on any other computers?
Some additional information will help determine the cause of the behavior.