A few recent news reports have billed 2010 as a slow year so far for stocks. The S&P 500 index, which tracks large American companies, has returned just over 3%. Granted, that s less dramatic than the 37% loss the index suffered in 2008 or the 26% comeback it made last year. But a 3% return in 10 weeks works out to more than a 15% return over a year, if the pace is sustained. The average yearly return for stocks (compounded) since 1871 is not quite 9%. So stocks aren t as sleepy as they seem.

The companies below are off to a rough start. Through mid-March, they re the worst three performers in the S&P 500. For them, that s largely a negative sign. Stocks with lousy price momentum in recent months tend to underperform the market over the next few months, studies show. Of course, patient value investors needn t worry about short-term price momentum if they see a good deal. Here s a closer look at what has gone wrong recently for each company, and whether the current price represents a bargain.

H&R Block

Down 26%

Few companies are more seasonal than H&R Block (HRB) . More than half its yearly sales and almost all of its profits tend to come during its fiscal fourth quarter, which runs through the end of April, just past the deadline for filing personal tax returns. On March 8, when the company reported mixed results for its third quarter (disappointing sales and decent profits), management didn t offer a full-year financial forecast, but Wall Street analysts suspect tax season is off to a slow start. Bad weather might have delayed some filings, but more important, a high unemployment rate might have reduced the number of returns, or at least convinced more filers to do it themselves. Meanwhile, past efforts by the company to diversify into other financial services and smooth quarterly returns aren t providing much benefit mortgages in particular have disappointed. Management is at least working to improve core tax services by sprucing up offices and hiring fewer new tax preparers but spending more to train them. And H&R s own financials look strong. Cash exceeds debt, free cash flow is greater than paper profits, the company is repurchasing plenty of stock and shares yield 3.6%.

KLA-Tencor

Down 19%

KLA-Tencor (KLAC) makes equipment used by computer chip manufacturers. Its sales plunged nearly 40% during its fiscal year ended June 2009, but are expected to increase 17% this year. On Monday, shares of KLA and other chip equipment makers tumbled after Taiwan Semiconductor Manufacturing (TSM), a major industry customer, announced that it will take a break from expanding, reducing equipment orders to near zero. On the bright side, KLA is easily the market leader in sales of equipment to detect chip defects and increase manufacturing yields, and such equipment will likely only become more important as chip complexity increases. For that reason, the stock research arm of Morningstar calls KLA one of our favorite companies in the semiconductor equipment space. The company has no net debt and its shares yield 2%.

Flir Systems

Down 18%

Flir Systems (FLIR) makes thermal imaging systems, which are used by soldiers and security workers to find or target bad guys and by engineers to detect or prevent structural problems. The recession has reduced spending among corporate customers, dampening Flir s growth rate. The company s sales jumped 38% in 2008, then just 7% last year, and are expected to increase 8% this year. Faster growth is needed to justify the stock s current price of close to 18 times this year s earnings forecast; the S&P 500 trades at less than 15 times forecast 2010 earnings. Josephine Millward of Benchmark Equity Research, who initiated coverage of the stock with a buy recommendation on March 9, wrote in a note to clients that Flir should return to a long-term growth rate of 15% to 20% once the economy improves. The company has no net debt and no dividend.