Updated from 1:30 p.m. EDT

Shares of iPass ( IPAS) were among the worst-performing technology stocks Thursday after the mobile networking company warned that second-quarter earnings and sales would fall well short of expectations.

iPass now expects to report pro forma earnings of 6 cents to 7 cents a share on sales of $40 million to $40.5 million. Analysts polled by Thomson First Call had expected it to earn 9 cents a share on sales of $43.8 million. The company said a "one-time operational decision" caused the expected second-quarter shortfall. Looking ahead, iPass said that it expects a sequential revenue increase of 3% to 6%, implying third-quarter sales of about $42.5 million. Analysts are expecting third-quarter sales of $47.1 million. Shares of iPass traded down $3.68, or 34.8%, to $6.91.

Amkor Technology ( AMKR) got pounded after the company warned that its second-quarter earnings would be below expectations. The company now expects to earn 6 cents a share vs. its previous estimate of 17 cents to 22 cents a share. The semiconductor assembly and test services company blamed the shortfall on an unfavorable product mix. Shares of Amkor Technology traded down $2.39, or 29.2%, to $5.79.

Shares of Colt Telecom ( COLT) got whacked after the company warned that it does not expect to meet second-quarter and full-year earnings expectations. It said that tougher-than-expected trading conditions, slower-than-anticipated uptake of its data products and disappointing performance of some higher-margin voice products caused it to issue the updated financial guidance. Shares of Colt Telecom traded down $1.95, or 33.1%, to $3.95.

Iona Technologies ( IONA) fell after it warned that its second-quarter financial results would not meet expectations. Citing slower-than-expected market adoption of its new technologies, Iona now expects to report a loss of 4 cents to 6 cents a share on sales of $15 million to $15.5 million. Analysts had expected the company to report a profit of 2 cents a share on sales of $18.2 million. Shares of Iona Technologies traded down 46 cents, or 11.3%, to $3.62.

Shares of MSC Software ( MNS) slumped after the software provider lowered its second-quarter financial guidance. It now expects to report break-even earnings to 3 cents a share on sales of $65 million to $67 million. It had previously said it would earn 6 cents to 8 cents a share on sales of $65 million to $70 million. Higher-than-anticipated legal fees and costs associated with an independent review pertaining to a Federal Trade Commission settlement contributed to the earnings revision. Shares of MSC Software traded down $1.13, or 12.6%, to $7.82.

Technology volume leaders included Microsoft ( MSFT), up 7 cents to $28.63; Intel ( INTC), down 58 cents to $27.02; Oracle ( ORCL), down 12 cents to $11.81; Cisco ( CSCO), down 59 cents to $23.11; Sun Microsystems ( SUNW), down 17 cents to $4.16; Applied Materials ( AMAT), down 62 cents to $19; Yahoo! ( YHOO), down $2.10 to $34.30; Lucent ( LU), down 17 cents to $3.61; and Nortel ( NT), down 17 cents to $4.82.

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