cause for/cause of

My dictionary (Macmillan) says "cause" means:
1. [C] an event, thing, or person that makes smth happen: The major cause of these accidents is driver's going too fast. <...> 1a. cause and effect <...>
2. [C/U] a reason for behaving in a particular way or for feeling a particular emotion: +for His departure was cause for celebration in the village. <...>

+ 2 more meanings.

I don't feel the difference between the first two meanings. Hence I cannot be sure if I chose the correct preposition.

Could you give me more examples for both meanings? Is it possible to devise a simple rule to choose the correct preposition? May be there are synonyms which are suitable in one case and not suitable in another...

By the way, as for the sentence 'The major cause of these accidents is driver's going too fast', is it correct to tell that 'the driver's going to fast was the reason for the accident' or that 'the driver was the reason for the accident'?

The Reform Party's landslide victory was cause for great euphoria across the nation.

The Reform Party's astonishingly irresponsible fiscal policies were the ultimate cause of the nation's rapid downward spiral into oblivion.

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As for rules, remember that English is not a rules-based language. I have no idea what kind of rule you could come up with here.