I'm having this same problem. When starting Frostwire the display is fine, but after minimizing/restoring it to/from the system tray the only thing that shows up is changing info (i.e. counters, percentages, etc...)

If I move the mouse over the tabs / menus they show up. When I select the between the tabs (i.e. "Search", "Monitor") the screen redraws and is readable.

I'm running the latest version of Java and the latest beta version of Frostwire.

Any help is appreciated.