Smack them around a bit...no just try to solve it by understanding both sides and try to come up with an agreement...if all else fails I usually give them a 2 day temp ban to let things calm.
Well first, your forum does have a strong "no fighting" rule, right? If it doesn't, make one XD Then be gentle-but-firm {heavy on the firm} and state that there will be penalties and bans for anyone who argues. Now, conference them and yourself in a 3 way chat or thread to try and work this out. Always be the mediator and make it clear that it can be worked out. And that it must be.
When I became acting head of my forum almost 2 years ago I inherited a forum fraught with drama and fighting. Turning a forum full of fights into a friendly well behaved one CAN be done. It's all about establishing firm limits and enforcing them consistently. It works with dogs, children, employees, and forum members. XD
Granted, the last argument that happened pretty much got solved before I even made it home from work that night. And had something to do with Olympic Hockey.
I try not to get involved unless they are blatantly and obviously disrespecting each other. If that happens then I send a link to the rules or recommend off-the-board communication (like IM, email, etc).
