Are they male or female?
Sad to say but generally speaking women will tend to bitch and hold a grudge longer than men - but if brought together under your mediation are also more likely to spill it all out and end up all huggy with each other.
If they are men, take em both down the pub for a long Friday 'lunch' and sort it over a macho pint.
If one's a man and the other is a woman - you're screwed mate, as neither is ever going to understand the point of view of the other - so depending on your sexual orientation, fire one of them.
