[Xmonad] MATLAB and Xmonad

Hi guys, I switched to Xmonad recently, after looking into wmii and dwm, and I am quite happy with it :) However, I tried starting up MATLAB today and it displays a huge gray screen. I thought it crashed during startup but when I clicked on where the menu bar should be, the menus actually open and are displayed properly. But everything else just doesn't draw in the MATLAB window. Does anybody has an idea what the problem might be (and/or give me hints how to provide some more useful information)? It looks like it's a problem with Xmonad. I fired up an Xnest with fvwm and MATLAB works fine there. And Xnest with wmii and MATLAB works as well. Thanks in advance, Christian