Do you have any 3rd party desktop applets or statusbar plugins running?

My guess is that your desktop runs out of memory. MediaBox is highly optimized to minimize memory
consumption and is about on par with YouAmp in terms of memory consumption, but some
graphics are stored on the X server side (Xomap) for best performance.

It would be interesting to know at what stage MediaBox crashes your desktop. Is it during startup, or when playing media, or... ?