Shares of SigmaTel ( SGTL) were among technology's losers Thursday, slumping 13% after the chipmaker slashed its first-quarter guidance. The company now sees sales of $30 million to $35 million, down from an earlier view of $52 million to $60 million. Analysts polled by Thomson First Call had an average forecast for sales of $54.5 million. SigmaTel said its results were hurt by order pushouts, a decline in flash prices and slower-than-expected adoption of its STFM 1000 product, which was plagued by firmware issues and delays in reference designs. The company also said a tax issue could lower earnings by as much as 50 cents a share. "The company is evaluating alternatives relative to this tax strategy and is not providing specific revised EPS guidance at this time," it said. In late January the company predicted that it would post a loss of 1 cent to 8 cents a share, excluding items, for the first quarter. Shares were trading down $1.36 to $8.77. Nokia ( NOK) rose 4% after the cell phone maker lifted its forecast for 2006 mobile device market volume. The company now expects handset volume to rise 15%, up from an earlier view of 10%. Nokia attributed the better-than-expected outlook to strong subscriber growth. Shares were up 97 cents to $21.19. Shares of ATI Technologies ( ATYT) rose 8% after the graphics-chips maker's second-quarter results topped forecasts. The company earned $34.1 million, or 13 cents a share, on revenue of $672.4 million. Excluding items, the company earned $44.8 million, or 17 cents a share, for the February quarter. Analysts expected earnings of 11 cents a share, before items, and revenue of $648.4 million. During the year-earlier period, ATI earned $57.2 million, or 22 cents a share, on revenue of $608.2 million. Excluding items, the company earned $65.4 million, or 25 cents a share, in the year-ago period.