Even if I could not yet solve the problem to my full satisfaction. I at least found a workaround to get the dfu-util working inside VMware Fusion. Now I’m able to flash it from inside VMware and from Mac OS X.

The workaround consits of using dfu-util form Mac OS X to get the openmoko ready to flash. I posted the Instructions under http://wiki.openmoko.org/wiki/MacOS_X. But I still hope I will find a real solution for the problem. If somebody has some hints please contact me.