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 Molina Healthcare (NYSE: MOH) plummeted 30% on Thursday after the health insurer pulled its 2012 profit outlook due to medical cost uncertainties in Texas.

So what: Molina has been expanding rapidly its Texas, but higher-than-expected member claims from Hidalgo and El Paso are triggering serious concerns about its profitability going forward. Naturally, the fears are carrying over to other health insurers with exposure to those markets, as the likes of Centene (NYSE: CNC) and Amerigroup are down 13% and 4%, respectively.

Now what: To rectify the situation, Molina plans to set new premium rates on September 1 and control costs as best as it can, as well as asking the state of Texas for some relief in its rate-setting assumptions. Of course, if management can't turn things around in Hidalgo and El Paso, Molina can simply choose to leave those margin-squeezing markets. So while the Texas trouble will certainly put pressure on Molina in the short-term, it's likely not as devastating to the long-term bull case as today's sell-off suggests.

Interested in more info on Molina? Add it to your watchlist.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.