This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Also, you might try checking the preferred size of the incoming component. If it was designed to be placed in an expanding–type layout, such as the Center section of a BorderLayout, you may need to use a different layout manager and/or provide size hints.