Updated from 4:03 p.m. EDT

Traders endured a choppy session Wednesday, but a surge in the final half-hour of action lifted the major averages and allowed blue-chips and tech stocks to end with modest gains.

The Dow Jones Industrial Average closed up 84.95 points, or 1%, to 8957.02. The Nasdaq was higher by 32.51 points, or 2.4%, at 1409.24, and the S&P 500 added 11.91 points, or 1.3%, to 949.34.

Corporate scandal reclaimed the headlines, as former Enron executive Michael Kopper agreed to plead guilty to criminal charges stemming from the government's investigation of the bankrupt energy merchant. It's the first prosecution in the company's collapse. Kopper pled guilty to two conspiracy charges and arranged to surrender $12 million in assets.

Elsewhere, AOL Time Warner ( AOL) agreed to buy out AT&T's ( T) stake in their Time Warner Entertainment venture. Shares of AT&T rose 9%, and AOL climbed 7%.

On the earnings front, retailers remained in the spotlight. Sports Authority ( TSA) posted in-line results, but said it would drop plans to offer $90 million in stock. On Tuesday, the company said its chief operating officer was resigning. Investors on the whole didn't like the news, and shares of Sports Authority lost 18% to $7.10.

Among other chain-store operators with quarterly results, closeout retailer Big Lots ( BLI) exceeded analysts' forecasts. Talbots ( TLB), a seller of clothes for women, said revenue fell in the latest quarter but earnings were a penny better than estimates. Big Lots declined, but Talbots was higher.

One of the worst performers in the group was RadioShack ( RSH), which sank 16% to $24.21 after the electronics merchant said second-quarter earnings will fall short of estimates. Overall, the sector was stronger, as the Dow Jones U.S. Retail Index climbed 1.5%.

Meanwhile, despite a decline in the semiconductor-equipment book-to-bill ratio to 1.16 in July from a revised 1.26 in June, the chip sector was gaining ground. The Philadelphia Stock Exchange Semiconductor Index advanced 4.7%.

Treasuries were lower around 4 p.m. EDT. The 10-year note was down 13/32 at 101 12/32 to yield 4.202%. The 30-year bond was off 22/32 to 105 13/32 and yielding 5.015%.

European shares were mainly higher following solid earnings from insurer Axa and airline Deutsche Lufthansa. London's FTSE 100 slipped 0.1% to 4365, and Germany's Xetra DAX gained 2.6% to 3868. In Asia, Japan's Nikkei rose 0.2% to 9643, while Hong Kong's Hang Seng was little changed at 10,402.