A Black Friday for Stocks

SanDisk dove 15.1% to $42.71, shares of AMD slid 5.5% to $13.80, and Xilinx was lower by 2.5% to $25.31.

Oil giant Schlumberger (SLB Quote) posted a 35% rise in profit from a year ago, handily beating estimates. Boston Scientific (BSX Quote) swung to a third-quarter loss, but it surpassed the Thomson First Call consensus of 7 cents a share on an adjusted basis.

Schlumberger, though, tanked 11% to $99.32, while Boston Scientific rallied 4.1% to end the day at $14.42.

Elsewhere, Wachovia (WB Quote) echoed the same issues other lenders had last quarter, reporting earnings that missed estimates due to writedowns related to the recent credit crisis. Wachovia was off $1.74, or 3.6%, to close at $46.40.

The major averages were further upset after Federal Reserve Chairman Ben Bernanke offered cautious comments on the central bank's ability to depend on economic data going forward during a speech in St. Louis.

"The fact that the public is uncertain about and must learn about the economy and policy provides a reason for the central bank to strive for predictability and transparency, avoid overreacting to current economic information, and recognize the challenges of making real-time assessments of the sustainable level of real economic activity and employment," Bernanke said.

"Most fundamentally, our discussions of the pervasive uncertainty that we face as policymakers is a powerful reminder of the need for humility about our ability to forecast and manage the future course of the economy," he concluded.

Overseas markets were lower. In Asia, Japan's Nikkei 225 slid 1.7%. In Europe, London's FTSE 100 dropped 1.2%, and Germany's Xetra Dax was off 0.5%.