The small-cap sector largely managed to stay afloat Thursday amid surging names like Acme Packet ( APKT).

The Burlington, Mass., company racked up 22.6% gains on second-quarter non-GAAP income of $5.7 million, or 9 cents a share. That tops the average analysts' estimate by a penny, according to Thomson Financial. Shares were up $2.35 to $12.77.

San Diego's Cubic ( CUB), which makes defense electronics and transportation-fare-collection systems, bounced 19.4% to $32.70 on a decisive earnings beat. Fiscal third-quarter earnings rose sharply to $11.2 million, or 42 cents a share, from 22 cents a share a year ago. Analysts were looking for 33 cents a share.

Both Acme and Cubic helped to prop up the Russell 2000, which was lately climbing 1.7 points, or 0.2%, to 779.62. The S&P SmallCap 600 added 0.4% to 412.53.

Elsewhere, BluePhoenix Solutions ( BPHX) rode high after the Israel-based business-software company inked a letter of intent to buy Texas-based Amalgamated Software North America. The deal is worth $9.5 million in cash, in addition to an earn-out for ASNA shareholders contingent on achievement of certain profit targets. BluePhoenix shares jumped $1.76, or 15.6%, to $13.06.

Pozen ( POZN) shares took a 43% free fall, however, after the Food and Drug Administration said it and partner GlaxoSmithKline ( GSK) need to collect more safety data on their proposed migraine drug Trexima. North Carolina-based Pozen lost $7.50 to $9.95; Glaxo ticked up 0.7% to $51.97.

In earnings, Liquidity Services ( LQDT) plunged some 26% after coming in a penny under consensus for per-share earnings in the fiscal third quarter, as well as pegging adjusted next-quarter income at 9 cents a share. Analysts looking for 12 cents. Shares of the Washington, D.C.-based auction-Web-site operator were changing hands at $12.42.

And toymaker RC2 ( RCRC) lost 19.5% after chopping at least 45 cents off its full-year income guidance for a range between $2.05 to $2.15 a share -- at least 50 cents under Wall Street expectations. Results for the second quarter, moreover, missed substantially on both top and bottom lines. Shares slumped $6.99 to $28.90.

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