Can't enter Polish characters after setting keyboard layout

[Starlight]

Hi, I have a problem with Ubuntu on my iBook. I wanted to be able to enter Polish characters, so I opened System -> Preferences -> Keyboard, and there I added the Polish layout. According to the layout illustration, it was correct. Then, in layout options I set the "win" keys as compose keys. However, I can't enter Polish characters... when I press the compose key, and I press a character, nothing happens. While I press the character again, while still having the compose key pressed, I get a foreign character sometimes, but not Polish characters. I tried setting "keyboard model" to different Apple models, and some generic ones, and it didn't change anything. How can I set it up correctly so that I can enter Polish characters?