If Simkl Tray says that the password is incorrect, and you tried to change keyboard layout from Spanish to English (when you enter the password), then the problem is not in Windows Live Messenger but in Simkl Tray.
1) You can try uninstalling Simkl Tray and completely delete Simkl folder in Program Files, then install Simkl Tray again.
2) If it still says that you're entering a wrong Simkl password, could you please tell us if your password contains any "special Spanish characters" (not from English alphabet) perhaps the program understands them incorrectly. You can also try changing your password at
http://passport.simkl.com/profile/edit/ that does not contain any special characters.