Crossover 6.0 is incompatible with Build 204 according to my testing.
Symptom: After updating to Build 204 when restarting Metatrader 4, no application window appears.
Launching Metatrader 4 from commandline or button does not work. Fresh installation does not work. Debugger starts as soon as Metatrader 4 is launched.
A workaround is known.