Updated from 2:08 p.m. EDT

Shares of

Adtran

(ADTN) - Get Report

were among the worst-performing technology stocks Tuesday, falling 16.4% after the company warned that fourth-quarter earnings and sales would fall below expectations.

The network-equipment company forecast earnings of 16 cents to 18 cents a share on sales of $100 million to $104 million. Analysts surveyed by Thomson First Call had been expecting earnings of 25 cents a share on sales of $119 million.

Adtran said "bookings have been weak during the quarter in the midst of a pause in our markets. We believe this pause will be short-lived as consumer demand for broadband services continues to grow and as business spending begins to improve." Full results will be released on Jan. 25. Shares traded down $3.58 to $18.23.

MicroStrategy

(MSTR) - Get Report

fell 14.7% after the company's chief financial officer resigned. Arthur Locke III, who most recently served as a member of MicroStrategy's finance team, will replace Eric Brown, who also served as president. In addition to his CEO duties, Michael Saylor will assume the position of president. The departure of Eric Brown is effective Dec. 31.

Brown is leaving the company to join

McAfee

( MFE), where he will serve as CFO. In response to the resignation, Wedbush Morgan Securities downgraded shares of the stock to hold from buy, lowering the price target on the company to $60 from $65 a share. First Albany lowered its rating on the stock as well, taking the stock to neutral from strong buy. Shares of MicroStrategy traded down $9.67 to $56.22.

Shares of

Tekelec

( TKLC) fell 8.6% after the telecommunication products company announced the resignation of its CFO. Paul Pucino, whose resignation is effective on or about Jan. 31, will be leaving the company to assume the position of CFO at

Digital Insight

( DGIN). Tekelec already has begun to search for Pucino's replacement, it said. Shares traded down $1.83 to $19.46.

Manchester Technologies

( MANC) rose 66.3% after the company's first-quarter earnings jumped by more than 200%. Excluding items, the display technology company earned $1.8 million, or 21 cents a share, on sales of $46.9 million.

A year ago, the company earned $844,000, or 10 cents a share, on sales of $45.4 million. Sales of the company's display technology products jumped by 12% in the latest quarter, which helped offset a decline in computer hardware sales to dealers and systems integrators. Shares traded up $3.19 to $8.

Shares of

ProQuest

( PQE) rose 17.8% after the company announced the acquisition of Voyager Expanded Learning, a privately held education services company. Under the terms, ProQuest will pay Voyager $340 million in cash and $20 million in stock. The deal, which is expected to close during early 2005, is expected to be accretive to earnings for the full year. As a result of the acquisition, ProQuest expects 2005 earnings of $2.20 to $2.40 a share. Analysts had been expecting earnings of $2.01 a share on sales of $491.3 million. Shares traded up $4.84 to $32.11.

Other technology volume leaders included

Microsoft

(MSFT) - Get Report

, down 2 cents to $27.23;

Sirius Satellite Radio

(SIRI) - Get Report

, down 9 cents to $7.95;

Oracle

(ORCL) - Get Report

, down 40 cents to $14.23;

Intel

(INTC) - Get Report

, up 61 cents to $23.24;

Lucent

( LU), down 7 cents to $3.64;

Symantec

(SYMC) - Get Report

, down $5.41 to $27.45; and

Nextel Communications

( NXTL), unchanged at $29.99.