LONDON -- The FTSE 100 (INDEX: ^FTSE) is flat as of 8 a.m. EDT after the European Central Bank announced that, as expected, it will cut its main refinancing rate from 0.75% to 0.5% -- a record low. Yesterday's optimism from the Federal Reserve's openness to further economic stimulus was tempered by weak U.S. jobs news, and that has helped foster an air of uncertainty today.

We've had some substantial share-price falls today as well. Here are three constituents of the various indexes that are falling.

Imagination Technologies
A year-end profit warning sent Imagination Technologies Group shares crashing 19.4% to 342 pence this morning. Several deals at the chip maker have been delayed, and that is going to result in a fall in licensing revenue for the year to about 27 million pounds, down from last year's 34 million pounds. However, the firm stressed that this is just a short-term timing issue and said licensing revenue for 2014 should be back up to the 30 million pound to 35 million pound range.

Unit shipments continue strongly, with more than 500 million units expected to be shipped over the full year, and royalty revenue should be in line with previous expectations.

Rolls-Royce
Rolls-Royce Holdings shares have fallen modestly after the firm announced the unexpected departure of aerospace president Mark King. He will be replaced by Tony Wood, currently president of the marine division.

In other news, first-quarter trading has been in line with expectations, and the company is still on for "modest growth in underlying revenue and good growth in underlying profit." Rolls-Royce has also won some new contracts, including an order from International Airlines Group for Trent engines to power 18 Airbus A350-1000 planes.

Howden (HWDN -1.68%)
Shares in Howden Joinery Group have dipped 0.4%, even though the company issued an upbeat interim update -- but the shares have more than doubled over the past 12 months, so this might be no more than profit-taking.

Revenue for the first 16 weeks of the year was up 9.3% overall and up 7.6% on a same-depot basis. The reporting period did include an extra week of trading over last year, and accounting for that brings revenue growth down to a still-respectable 4.1% over the past three months. Looking forward, Howden is planning to open 20 to 30 new depots this year.

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