As mention above two unspayed females Is more than likely your problem. That said getting them fixed at this time may not fix the problem. You need to keep them seperatated. Fixing such a problem is not possible over a bb like this one because. Limit space to express training/behavior mod plans. and even more important no direct observation of the dogs. I can however recommend the following resources
FIGHT! A PRACTICAL GUIDE TO THE TREATMENT OF DOG-DOG AGGRESSION
a fair review of Fight!
agheh yahoo bgroup
Directory of Certified Animal Behaviorist
Certified Member Listing of Dog Behavior Consultants
American Society of Veterinary Behaviorist - Find a Behaviorist
Some link to articles on Female/female dog aggression and in a word success in dealing with the problem other than issolation is not good.
Feisty Females
Dangerous Aggression Between Two Female Dogs
Aggression Between Dogs
Characteristics, treatment, and outcome of 99 cases of aggression between dogs