Small-cap stocks followed the broader indices downward Monday. The Russell 2000 was off 1.4% at 743.16, and the S&P SmallCap 600 lost 1.3% to 385.39.

Among the biggest losers was

ACI Worldwide

(ACIW) - Get Report

as the maker of electronic-payments software announced fourth-quarter earnings would be well below analysts' outlook. ACI expects a pretax loss of $10.4 million and a 4% year-over-year decrease in revenue to $85 million, whereas analysts surveyed by Thomson Financial were expecting $100 million. The company's announcement of a strategic partnership with

IBM

(IBM) - Get Report

-- under which Big Blue will receive warrants to purchase up to 8% of ACI's shares, half at $27.50 a share and half at $33 -- offered little consolation to investors, however, and shares sank 18% to $19.27.

Boulder, Colo.-based maker of broadband equipment

Carrier Access

( CACS) also fell after announcing it will be bought by

Turin Networks

for $93 million, or $2.60 a share, a slight premium over Friday's closing price of $2.50. Shares dropped 11% to $2.22.

On the winning side,

American Dental Partners

( ADPI), a Wakefield, Mass., provider of business services to dental group practices, jumped 25% on unusually high volume to $6.30 Monday. The move was a rebound from last week, when the stock sold off heavily on Thursday's news the company had lost a $130 million lawsuit against one of its clients.

Meanwhile, shares of Chinese wireless entertainment provider

KongZhong

(KONG)

climbed 17% to $6.34 as the company raised guidance for the fourth quarter of 2007. KongZhong now predicts revenue of $18.5 million to $19.5 million, up from a previous range of $17.5 million to $18.5 million.

Also rising was

Delek U.S. Holdings

(DK) - Get Report

. The Brentwood, Tenn.-based oil and gas refiner jumped 10% to $19.73 on a Citigroup upgrade to buy from hold that reflected the bank's broader bullish outlook on refiners.