Updated from 2:49 p.m. EST with new stock prices

Small-cap stocks were tumbling Friday along with the broader market. The Russell 2000 was down 0.12% to 695.45, but the S&P SmallCap 600 was up 0.12% to 368.82.

United Natural Foods ( UNFI) shares fell 24.2% to $18.07 after the Davyille, Conn., natural and organic food distributor reported fiscal second-quarter 2008 earnings and cut guidance Thursday after the close. Excluding acquisition-related dilution of earnings, the company reported income of $12.4 million, or 29 cents a share, vs. $10.9 million, or a quarter a share, in the year-ago quarter.

Analysts surveyed by Thomson Financial were looking for 30 cents a share. United Natural also lowered full-year EPS guidance for 2008 to $1.12 to $1.14 a share from a previous forecast of $1.40 to $1.45 a share. Piper Jaffray downgraded the stock to neutral from buy.

Meanwhile, shares of Cbeyond ( CBEY), an Atlanta provider of voice-over-Internet protocol services, slumped 20.2% to $18.76 on last night's fourth-quarter earnings.

Including a $9.6 million benefit from the expected future realization of operating loss carryforwards, Cbeyond posted income of $12.5 million, compared with $4.3 million a year ago. Pointing to a "continued challenging economy during 2008," the company predicted full-year revenue between $355 million and $360 million, short of the Street's outlook of $364.4 million.

Pekin, Ill.-based Aventine Renewable Energy ( AVR), an ethanol maker, also fell after the company warned of delays in construction of two new properties. For the fourth quarter, profit fell to $3.3 million, or 8 cents a share, vs. $12.8 million, or 30 cents a share, in 2006. Analysts polled by Thomson Financial were looking for a loss of 3 cents a share, but the company's warnings that its capital was invested in faltering auction-rate securities sent investors running, and the stock fell 18.4% to $6.94.

On the winning side, shares of Navigant Consulting ( NCI) climbed on last night's earnings. The Chicago provider of dispute, financial, regulatory and operations advisory services posted adjusted fourth-quarter net income of $10.3 million, or 22 cents a share, vs. $15.5 million, or 28 cents a share, in 2006. Analysts had forecast 14 cents a share.

Also gaining was Force Protection ( FRPT). The Lasdon, S.C., maker of mine-resistant, ambush-protected vehicles (MRAPs) announced a $115.2 million deal for the sale of 174 of its vehicles. The MRAPs will be bought by the U.K. under the U.S. Foreign Military Sales program. Force Protection also reported receipt of an $8 million order from the Italian Ministry of Defense. Shares jumped 9.8% to $4.70.

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