ceiling fan wiring
From the info you supplied, I would guess you are frome Europe. My reasoning is that in Europe, the brown wire is a ground, meaning " to earth". If so are you sure the fixtures you installed are 110 Volt and not 220V? Without more info I cannot diagnose your problem. But for a stab, check the wiring coming into the box and ascertain that there are no bare wiries touching the box, as this happens over a period of time.
Talk to me, Len
The brown wire could be a "hot" wire that separately controls the fan or light. It also might be an unswitched "hot" wire that allows the light to be switched but the fan to continue blowing even when the light is turned off at the switch.
If the brown wire is an alternate "hot" wire, then connecting it to the ground wire of the fan that would cause a short.
In any case, determine which wire is connected to the switch. Use a tester on the brown and white wires to see if the brown is "hot." If so, then switch the switch off and test it to see if the switch is connected to it.
Also test the black wire to see if it is connected to the switch. (Turn it on, then touch the tester to the black and white wires to see if the tester glows. If so, then turn the switch off, then do it again to see if the tester then does not glow. If it does, then the black wire is switched.)
It is kosher to hook both the fan and the light up to the same hot wire coming into the box. That is not the problem.