Some weeks ago, heart surgeon Don Williams wrote a letter to the chairman of the board of the Miami Beach-based Mount Sinai Medical Center, complaining about the institution where he's worked for almost 20 years. That a prominent surgeon would write a scathing letter about his boss is a testament to the extent of the problems and discord at Mount Sinai. The once-thriving institution now persistently loses money, has only two of every five of its licensed beds occupied, and carries more than $250 million in junk bond debt.