US markets have opened lower as investors take a dim view of Hewlett Packard's latest acquisition and send its shares down 20%.
US manufacturing data has sent markets plunging again, with the S&P 500 down 4.5% and the UK and Europe also tumbling.
US investors jettisoned shares in early trading following a warning from consumer giant Walmart, piling on the pressure following weaker than expected German economic growth.
GMO's Jeremy Grantham has said the S&P 500 is still heavily overvalued, and "worth no more than 950".
US markets have opened higher after a calmer atmosphere saw the FTSE 100 recover the day's losses.
Bank of America's share price fell by 20% as US financials were routed in Monday trading over growth fears and S&P's downgrade of the US credit rating.
Heavy losses in the battered US markets have spread to the UK and sent the index of 100 leading shares down more than 3%.
European and Asian stock markets declined sharply in Wednesday trading, mirroring overnight falls in New York, on concerns the US recovery is faltering.
The FTSE has plunged into negative territory after disappointing US jobs data reignited fears over the economic recovery.