SAN FRANCISCO — Mike Lynch was in a business meeting in London on Tuesday when his phone buzzed.

A text message from a friend informed him that Hewlett-Packard was taking an $8.8 billion charge. A few minutes later, another message said HP was putting most of the blame for the write-down on accounting problems at Autonomy, the company Lynch cofounded and sold to HP last year for $10 billion. There was talk of potentially criminal activities.