When characters like '@','€','|' or 'æ' are used in the password of a Minecraft/Mojang-Account the login will not work in the launcher on a linux system (on windows it works fine).
Instead it will say: "Sorry, but your username or password is incorrect! Please try again. If you need help, try the 'Forgot Password' link."

The login on the Mojang/Minecraft-website works so I guess there is some encoding issue with the launcher.