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 insurer Genworth Financial (NYSE: GNW) were rocketing higher today, gaining as much as 16% in intraday trading after a Citigroup (NYSE: C) analyst put a buy rating on the company's shares.

So what: According to Bloomberg, Citigroup's Colin Devine had a sell rating on Genworth shares between August 2009 and earlier this month. Now he's gone the full 180 and slapped a buy on the stock. Why? The simple answer is that shares are cheap.

Specifically, Devine thinks the market has overblown the possibility that Genworth will go belly-up. The U.S. mortgage market that Genworth insures is far from healthy -- further losses are likely ahead and new business won't exactly be booming. But with the stock badly beaten down, Devine thinks the opportunity outweighs the risk.

Now what: As an owner of Genworth stock myself, I'm certainly happy about what the stock's doing today. However, it's important to keep in mind that this doesn't change the fundamental picture at Genworth -- it's just one particular view on that fundamental picture. While Devine's bullish call might be a good reason to give the company a second look, investors will want to make sure they have their own buying thesis before joining the crowd today in the buying frenzy.

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