LONDON -- Shares in Electrocomponents (LSE: ECM.L) plunged 8% to 202 pence after the distributor of the Raspberry Pi computer warned that full-year profits would be below market expectations.

The company, which operates under the banners of RS Components in the U.K. and Allied Electronics in the U.S., said first-half sales are likely to be flat as a result of challenging economic conditions.

Electrocomponents said, "Group gross margin is likely to be around 1.2% points below the prior year, affected by the increased use of customer discounts, stronger performance from lower-margin technologies, including Raspberry Pi, and adverse foreign exchange movements." It also said operating costs are expected to be 4% higher. However, it added that the additional cost will be skewed to the first half. Consequently, pre-tax profit for the first six months of the year comes to around 40 million pounds compared with 59 million pounds last time.

That said, Electrocomponents believes that second-half profits should benefit from actions to improve operating margins. Nevertheless, it reckons that given the worse-than-expected first-half performance, and assuming no change in market conditions, it still expects full-year headline pre-tax profits to be lower than market forecasts, which call for about 110 million pounds.

This morning's trading update from Electrocomponents illustrates how shares can sometimes disappoint investors -- especially income seekers -- given the company's attractive prospective dividend yield of 5.5%. If you're on the lookout for more reliable income shares, look no further than ace stock-picker Neil Woodford, who has a record of avoiding such losers. Indeed, Woodford has delivered an impressive 347% total return during the 15 years to the end of 2011. You can discover the shares he now holds -- and which losers he has avoided -- within "8 Shares Held By Britain's Super Investor." You can download this free Fool report about market legend Woodford today, but hurry -- the report is available for a limited time only.

Investing is by no means easy in today's uncertain economy. That's why we've published "Three Top Sectors" -- our guide to three favorable industries. This free report will be dispatched immediately to your inbox.

Further Motley Fool investment opportunities:

David does not own shares in Electrocomponents. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.