It used to take less than an hour to backup this same system, now it takes several

It used to take less than an hour to backup this same system, now it takes several hours. I have the same amount of data and am still hooked up to high speed USB 3.0. I am using the Advanced version now had to reinstall due to a corruption. The bar does not seem to be moving, showing that little or no progress has been made in the backup though it does appear to have gotten about 60-percent of the way through. Please help.