Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Computer Sciences Corp. (NYSE: CSC) plunged 14.5% in intraday trading today after the company reported earnings and lowered guidance for the current quarter.

So what: Reported EPS of $1.54 beat the consensus estimate of $1.48. However, "sluggish" contract signings in the North American public sector led the company to lower EPS guidance for the fiscal year (with just the current quarter to go) to $5.20 versus a consensus estimate of $5.39.  

Now what: Because $3.64 of EPS is already in the bag year-to-date, the estimate for the current quarter is likely to drop from $1.81 to around $1.56. With government spending under pressure, the weakness could continue for an extended period, and earnings estimates beyond the current quarter are likely too high. A P/E ratio of 11.1 with a 1.4% dividend yield may seem attractive, but investors might be better off waiting for the news flow to turn positive before jumping into the stock.

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Fool contributor Cindy Johnson does not own shares of any company named above. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.