Beth Israel Deaconess Medical Center is notifying more than 2,000 patients that some of their personal information may have been stolen from a hospital computer. The hospital said yesterday that an unnamed computer service vendor had failed to restore proper security settings on a computer after performing maintenance on it. The machine was later found to be infected with a virus, which transmitted data files to an unknown location. The computer contained medical record numbers, names, genders, and birthdates of 2,021 patients, as well as the names and dates of radiology procedures they had undergone. But the computer did not contain the patients' financial data or their Social Security numbers.