A friend on mine asked me if I had any ideia how can a Sharepoint site be in one language (Portuguese) and the correspondant My sites be in another (English).
The reason was that the Sharepoint was in English and had the Portuguese language pack installed, the result of this is that when a user creates his My Site it will be done in English and not Portuguese. Why?
Well, in the Shared Services, User Profiles and My Sites there is an option My Sites Settings. There you have a check box to enable the user to choose the language for their personal site, it should be unchecked . . .
So to sum up, to solve the problem you can check that option, and the users will be asked, on the creation of the personnal sites, in which language they choose.
It isn´t rocket science, but it solves problems.