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: Fortinet (Nasdaq: FTNT) dropped 24% in intraday trading today after reporting better than expected earnings and forecasting a marked slowdown in revenue growth for the third and fourth quarters.

So what: Second-quarter EPS of $0.09 rose 50% year over year and beat the consensus estimate of $0.08. Revenue grew 35% year over year, taking average revenue growth for the first half to about 34%.

Now what: The midpoint of management guidance called for revenue growth of only 20% in the third quarter and 24% for 2011. During its earnings call, the company disclosed economic and execution challenges in the Europe, Middle East, and Africa region. The disappointing EMEA growth in the second quarter and revenue guidance -- with growth slowing markedly this quarter and picking up a bit in the fourth -- suggests the challenges may be greater than management is letting on ... or realizes.

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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.