Sprint shares were up following a Wall Street Journal report that activist investor Ralph Witworth is pressuring Chief Executive Gary Forsee and other directors regarding company strategy. Spring shares gained 74 cents, or 3.9 percent, to $19.50 in midday trading.

The S&P 500 was up 2.45, to 1,542.06 at midday.

Also gaining were shares of Forest Labs Inc., following an upgrade to "Buy" from "Neutral," from FTN Midwest analyst Timothy Chiang. Shares gained $1.19, or 3.1 percent, to $39.59.

Shares of Fannie Mae added $2.15, or 3.3 percent, to $68.19. Democrats have repeated calls to the White House to increase the portfolio caps for the government-backed home-loan finance company in response to the mortgage crisis.

Lennar Corp. was among the midday laggards, after UBS analyst David Goldberg said it appears that home prices are deteriorating worse than he expected for the Miami homebuilder, and he expects recent gains in the sector's stocks to reverse themselves. Shares declined $1.62, 6.3 percent, to $24.20.

Pulte Homes Inc. shares fell 94 cents, or 5.9 percent, to $15.02, as the entire sector slumped on concerns on continued price declines from several analysts.

Marriott International Inc. shares fell after the hotel operator issued a profit warning for the fourth quarter, the full year and 2008. Shares fell $2.32, or 5.2 percent, to $42.