Efforts to eliminate preventable hospital errors in Minnesota have taken on the appearance of the old arcade game Whac-A-Mole. Just as the state's hospitals reduce deaths or disabilities attributed to one type of mistake, another pops up. In the latest adverse-event report, released Thursday, Minnesota's hospitals showed substantial progress in reducing the number of painful and disabling pressure ulcers that patients suffer because of immobility in hospital beds. They also reduced the number of surgical errors such as procedures on the wrong body part. But increases in patient deaths or disabilities because of falls or medication errors countered the progress in other areas.