Shares of Rackable Systems ( RACK) plummeted in late trading Thursday after the company's weak guidance offset better-than-expected second-quarter earnings. The maker of servers and storage systems posted second-quarter earnings of $5.3 million, or 18 cents a share, down from with $1.2 million, or 7 cents a share, a year ago. Excluding items, earnings rose to $8.1 million, or 28 cents a share, from $2 million, or 12 cents a share, a year ago. Revenue increased 5% to $88.6 million. Analysts polled by Thomson First Call expected earnings of 22 cents a share, before items, on revenue of $84.3 million.

However, the company forecast third-quarter revenue of $80 million to $85 million in its conference call, according to Briefing.com, and warned that it sees declines in the server market. Analysts predict third-quarter revenue of $84.3 million. Shares tumbled $10.41, or 30%, to $24.50 after hours.

On Semiconductor ( ONNN) beat Wall Street's second-quarter earnings expectation, sending shares higher after hours. The company earned $67.5 million, or 19 cents a share, up from $13.5 million, or 5 cents a share, a year ago. The latest quarter's results include restructuring charges of about $3.3 million, or 1 cent a share. Analysts predicted earnings of 13 cents a share. Sales rose to $375.3 million from $302.8 million a year ago, topping Wall Street's forecast of $354.53 million.

Looking ahead, On Semiconductor forecast third-quarter sales of $405 million to $415 million, which is well above analysts' forecast of $372 million. Shares advanced 43 cents, or 7.1%, to $6.52 in after-hours trading.

Genesis Microchip ( GNSS) soared after the company beat Wall Street's fiscal first-quarter earnings expectations. The company earned $1.4 million, or 4 cents a share, down from $2.1 million, or 6 cents a share a year ago. Excluding items, Genesis Microchip earned 11 cents a share in the June quarter. Revenue totaled $55.9 million, down from $59.8 million a year earlier. Analysts were looking for break-even earnings and revenue of $57.9 million.

Genesis forecast fiscal second-quarter revenue of $67 million to $72 million. Analysts predict revenue of $67.3 million. Shares jumped $2.34, or 21%, to $13.55 after hours.

Sierra Wireless ( SWIR) shares plunged in late trading after the wireless-air-card maker offered lower-than-expected guidance. For the second quarter, the company swung to a profit of $3.8 million, or 15 cents a share, from a year-ago loss of $27.6 million, or 30 cents a share. Sales jumped to $55.2 million from $21.9 million. The results beat analysts' average estimate for earnings of 10 cents a share and sales of $52 million.

But for the third quarter, Sierra Wireless forecast break-even results and revenue of $51 million. Analysts had targeted earnings of 12 cents a share and revenue of $57 million. The company's shares slid $4.88, or 30%, to $11.37 after hours.

Shares of Deckers Outdoor ( DECK) got a boost after the footwear company topped second-quarter expectations. The company posted earnings of $2.7 million, or 21 cents a share, roughly flat with a year earlier. Sales increased 3.4% to $41.7 million. The results beat the company's guidance for a profit of 3 cents to 5 cents a share and revenue of $38 million to $40 million. Analysts anticipated earnings of 5 cents a share.

Deckers forecast third-quarter sales of $71 million to $74 million and earnings of 51 cents to 54 cents a share, lower than Wall Street's expectation for earnings of 68 cents a share and sales of $74.1 million. But Deckers raised its full-year outlook, predicting earnings of $2.39 to $2.45 a share, compared with previous expectations of $2.21 to $2.29 a share. The company raised its full-year sales projection to a range of $272 million to $278 million from its earlier guidance of $268 million to $276 million. Analysts, on average, predict 2006 earnings of $2.28 and sales of $274.4 million. Shares climbed $2.16, or 5.8%, to $39.30 in late trading.

Lawson Software ( LWSN) moved lower after hours as the business-software company announced changes in top management and said it expects to post a loss for its fourth quarter. Lawson's chief financial officer, Robert Barbieri, will be leaving the company Oct. 31. Barbieri, who has been financial chief since 2000, may elect to leave before that date, the company said. Separately, Lawson said it plans to eliminate its chief operating position, effective immediately. The company said it is in talks with Bertrand Sciard, who had held the position, regarding his transition and terms of his departure.

For the fourth quarter ended May 31, Lawson expects to report a loss of 7 cents to 9 cents a share, with revenue of $125 million to $126.6 million. The company attributed the loss to the inclusion of Intentia International, which it acquired in April. The company said its legacy business had a fourth-quarter profit of $7.2 million. Analysts, on average, expected a profit of 6 cents a share and revenue of 108 million. Because of the complexity related to accounting for Intentia, Lawson says it will seek an extension for filing its annual report with the Securities and Exchange Commission. Shares fell 40 cents, or 7.1%, to $5.25 after hours.