Do you mean there is Oil dripping from the cradel for the gearbox?There should be 2 engine mounts attached to this.
If it's the thing im thinking of(which it prob is going by your explanation)i will most probably be gearbox Oil,smell it and see-It should stink of cat piss if it is

It's either(as you say)A seal or the driveshaft has popped out a wee bit

Is it still dripping out?