[xmonad] Problem with popup menus in java application

Hi, I switched to xmonad, but since then I can't access the menus in JDownloader. The symptoms: I click on the File menu (or right click on a package to bring up the context menu), the menu appears, but as soon as I release the mouse button, the menu disappears, so I can't select anything. If I hold down the mouse button, and use the arrow keys + Enter, it works, but that's rather cumbersome. I already tried _JAVA_AWT_WM_NONREPARENTING=1 with OpenJDK and startupHook = setWMName "LG3D" with the Sun JRE. Any tips to solve this? Thanks.