The purpose of this study is to compare the safety and effectiveness of 2 treatments to prevent invasive fungal infections (IFI), which are infections caused by yeasts and molds that are common in patients with weak immune systems or transplant patients. AmBisome, a new treatment, will be compared to fluconazole, the traditional treatment for fungal infections caused by the yeast Candida. Treatment will only be given to liver transplant patients who are found to be at high risk for IFI. Liver transplant patients who are at low risk for IFI will be monitored but will receive no study medication.