SAN FRANCISCO (Reuters) - Vince Welnick, who took over as the Grateful Dead's keyboard player in 1990 after a succession of predecessors met untimely deaths, has died at the age of 55, according to an announcement on his Web site. "Vince passed from this earth on June 2, 2006 ... after a decade of battling tragedy while creating beauty and light around him," the announcement said. It did not give a cause of death. The San Jose Mercury News said he died in a hospital on Friday after being taken from his home in Forestville, California, and it quoted a...