Shares of

SafeNet

( SFNT) were among technology's losers Friday, tumbling 15% after the network security company lowered its first-quarter earnings guidance, announced the resignation of its chief financial officer and scotched a planned acquisition.

SafeNet expects adjusted earnings to be below its previous guidance of 29 cents to 37 cents a share. The company cut its revenue forecast to $63 million to $65 million from an earlier view of $65 million to $69 million. During the year-earlier period, the company posted revenue of $59.8 million. Analysts polled by Thomson First Call project earnings of 33 cents on revenue of $66.9 million.

The company said that CFO Ken Mueller will leave, effective immediately. Carole Argo, who served as financial chief from 1999 to 2004, will serve as CFO on an interim basis. Argo will continue in her current role as president as well. " We are making these changes in our leadership structure so that we can better focus appropriate skills on critical business areas," the company said.

Separately, SafeNet called off its planned $150 million acquisition of nCipher after U.K. regulatory authorities referred the deal for further review. The U.K. regulators said SafeNet and nCipher are two of the largest suppliers of hardware security modules in the country. "As the additional review process involves considerable expense and lasts for several months, SafeNet has decided to abandon this transaction," the company said. Shares were trading down $3.88 to $22.09.

Shares of

Internet Security Systems

( ISSX) fell 9% after the software company warned that first-quarter revenue would fall short of expectations. The company sees earnings of 20 cents a share, before items, which meets the low end of its guidance of 20 cents to 22 cents. The company estimates revenue of about $80 million, compared with its earlier forecast of $82 million to $85 million. Analysts project earnings of 22 cents a share and revenue of $83.9 million. Last year, the company reported first-quarter earnings of 19 cents a share on revenue of $76.8 million. The company plans to post its results on April 25. Shares were trading down $2.18 to $20.98.

WebMethods

( WEBM) rose 6% after the software company lifted its fiscal fourth-quarter projections. The company now sees earnings of 11 cents to 14 cents a share for the March quarter, up from an earlier view of 5 cents to 10 cents a share. The earnings will include a litigation settlement payment of $750,000. The company boosted its revenue estimate to $57 million to $59 million from its previous view of $52 million to $55 million. Analysts project earnings of 8 cents a share and revenue of $54.2 million. WebMethods plans to report its fourth-quarter results on April 27. Shares were trading up 51 cents to $9.24.

Shares of

Extreme Networks

(EXTR) - Get Report

fell 7% after the networking gearmaker warned that third-quarter revenue would fall short of its previous forecast. The company now sees revenue of $84 million to $85 million. The company's earlier forecast for the quarter ended April 2 called for a top line of $90 million to $95 million, while analysts projected revenue of $92.8 million. Extreme Networks said it was hurt by weaker-than-expected revenue in the U.S. and Japan. The company expects earnings to range from break even to 2 cents a share, excluding certain items. Analysts project earnings of 5 cents a share. The company plans to post its third-quarter results on April 25. Shares were trading down 34 cents to $4.75.

Transmeta

( TMTA) rose 5% after the chip company announced new contracts with

Sony

(SNE) - Get Report

. The agreements, which call for Transmeta to continue providing design and engineering services, will range from three months to one year, ending in March 2007. The agreements are part of a two-year design services agreement Transmeta and Sony signed in March 2005. Transmeta shares were trading up 11 cents to $2.13.

Other technology movers included

Sun Microsystems

(SUNW) - Get Report

, up 2 cents to $5.26;

Sirius Satellite Radio

(SIRI) - Get Report

, down 2 cents to $5.39;

Lucent Technologies

( LU), down 9 cents to $3.11;

Apple Computer

(AAPL) - Get Report

, down $2.51 to $68.73;

Intel

(INTC) - Get Report

, down 3 cents to $19.35;

JDSU

(JDSU)

, down 7 cents to $4.06;

Brocade Communications Systems

(BRCD)

, up 10 cents to $6.93;

Cisco Systems

(CSCO) - Get Report

, down 18 cents to $21;

Microsoft

(MSFT) - Get Report

, down 20 cents to $27.36;

Research In Motion

( RIMM), down $4.63 to $79.75;

Oracle

(ORCL) - Get Report

, up 1 cent to $13.81; and

Ciena

(CIEN) - Get Report

, down 6 cents to $4.85.