1) Workaround? - have maximizer in its own window and not a tab.
2) Resize the main desktop window (with maximizer as a tab) to something with more horizontal space and see if it shows up.
3) Set the preference rememberDesktopSize to false, if it is set to true.
I was kind of able to reproduce on Windows 7, Java 6 and it feels like one of those cases where when you try and put 10 lbs of Swing components into a 5 lbs container Swing just silently gives up and drops things.