I just changed the oil in my Honda 750 Shadow and switched to Synthetic Oil. As you mentioned this could cause the clutch to slip. Wel it 's slipping. What's the fix?

I'm assuming that you have a "wet" clutch, unlike most cars that have a "dry" clutch. "Wet" means that the clutch sits in the engine oil, "dry" ... that it doesn't!
It's very important that you use only oil specifically made for motorcycles if you have a wet clutch, synthetic or not. The formulation of the oil-additives is different if it is to be used with clutches.

Using "normal" "car" oil, whether it is synthetic or not, is highly likely to result in clutch slip.

If this is what has happened then I can only suggest this course of action:
> Drop that oil out and replace the oil filter
> Refill with cheap motorcycle oil
> Drive for 10 or so miles, get the engine nice and warm
> Drop that oil out
> Refill with cheap motorcycle oil again and drive 10 miles
>> Hopefully at this point the clutch slip will be gone
> Drop that oil out and change the oil filter.
> Now fill with "nice" motorcycle oil

Best of luck :-)
Alastair
(GPz1000)