[Lazarus] Two source code editors (bug?)

[Leonardo M. Ramé]

Hi, I don't know what I did to mess up my project, but now, every file I
open to edit, it's opened in a 2nd source code editor window, instead of the
main one.

This behavior only happens in one project. How can I force the IDE to
open pascal files in the first source code window?.

Thanks in advance,
-- 
Leonardo M. Ramé
http://leonardorame.blogspot.com