Los Angeles Times August 9, 1990, Thursday, P.M. Final NAMES IN THE NEWS; SINEAD O'CONNOR IS AILING Irish singer Sinead O'Connor is suffering from an undiagnosed illness that may cause her to cancel dates on her U.S. tour, a publicist said today. Concert-goers booed Tuesday after O'Connor cut short her performance by one song at the Star Lake Amphitheater in Washington County west of Pittsburgh. "She's got to take it easy," publicist Elaine Schock said in a telephone interview from Pelham, N.Y. "She wasn't feeling well, but went through the set anyway and cut the encore. That's not all that uncommon." About 6,100 people attended the show, paying $20.25 for tickets. O'Connor's recent single "Nothing Compares 2 U" and album "I Do Not Want What I Haven't Got" topped Billboard magazine's charts in both those categories.