Researchers at Boca Raton-based Nabi Biopharmaceuticals (Nasdaq-NABI) believed they hit a home run: A drug that could prevent the 90,000 deaths attributed to hospital-related staph infections each year. But StaphVAX struck out in the critical Phase III trials, sending the company's stock plummeting 70% in one day. Analysts are now pondering the future of the company many considered a biotech bedrock.