IMO, it sounds like a dominance issue between the two dogs, and yes, I would think that if a fight ensues once, it most likely could happen again, so, until a solution is found, if i were you, i would closely supervise the two of them, until they've established their ranks. And if you feel the need to intervene, just be sure to have a break stick ready and learn/know how to use it.
I, personally, would NEVER trust two dogs to not fight, ...
In the mean time, i would consistently (KEY, here) correct your male's behavior, and let him know that you will not tolerate it. I've heard of people using water guns, and spraying the dog EVERY time, putting the dog in another room, isolating it, or, if contained on a leash, snapping that leash to show your disapproaval, whenever this behavior occurs. Regardless of the method you choose to implement, it HAS to be consistent, to demonstrate to your dog that this behavior is NOT welcomed and must cease to continue. He HAS to learn that YOU deem it unacceptable, otherwise he will not understand, that a natural tendency for him, is angering you, not to mention annoying your female.
here is some general reading that may be helpful:
http://www.petplace.com/dogs/humping/page1.aspx
it's pretty basic, but it may point you in the right direction.
and i'm a HUGE fan of the NILIF program.
good luck!
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