Small-cap stocks got dinged along with the major indices Monday, selling off hard in the opening hour of trading and then mostly staying in the red. The Russell 2000 slipped 0.7% to 725.14, and the S&P SmallCap 600 sank 1% to 380.64.

Heading up the losers, car rental company

Dollar Thrifty

( DTG) lost 35% to $16.89 after slashing 2007 guidance Friday after the close. The Tulsa, Okla.-based company now predicts adjusted earnings ranging from 90 cents to 95 cents a share, down from a previous forecast of $1.75 to $1.85 a share. Analysts polled by Thomson Financial have been expecting a profit of $1.82 a share.

Also falling on lowered guidance was

Virgin Mobile

( VM). The Warren, N.J., wireless company predicts a full-year 2007 loss of $3 million to $6 million. The Street is looking for a loss of $3.5 million.

Several retailers lost ground on downgrades from Thomas Weisel. The bank downgraded Sandpoint, Idaho's

Coldwater Creek

(CWTR)

to underweight from market weight and cut its price target to $4 a share from $6 a share. The stock stumbled 16% to $5.90.

Charming Shoppes

(CHRS) - Get Coherus BioSciences, Inc. Report

suffered similarly, losing 16% to $5.81 after Thomas Weisel dropped the Bensalem, Pa., company to market weight from overweight, while maintaining its $6 price target. Charming Shoppes made national headlines over the weekend due to a fatal shooting at one of its Illinois stores Saturday.

TheStreet Recommends

Several companies managed to eke out gains on the tough day. Shares of Austin, Texas-based semiconductor company

SigmaTel

( SGTL) skyrocketed 60% to $2.86 on news that privately held

Freescale Semiconductor

will

buy the company for $110 million, or $3 a share in cash.

Activist investor Carl Icahn helped drive up the value of two small-caps when he bought a 9.5% stake in

Greenbrier

(GBX) - Get Greenbrier Companies, Inc. Report

. Icahn further expressed interest in a merger between the Oswego, Ore., railcar maker and St. Charles, Mo.-based

American Railcar

(ARII) - Get American Railcar Industries, Inc. Report

. Shares of Greenbrier jumped 20% to $25.00, while American Railcar climbed 17% to $20.70.

For more info on stocks held by Icahn, check out the Carl Icahn portfolio at Stockpickr.com.