Your stock just took a nosedive -- but don't panic. First, let's see whether it had good reason to fall. Sometimes, panic-fueled drops can make excellent buying opportunities. Here's the latest crop of cratered stocks that could provide a possibility for profit:

Stock

CAPS Rating (out of 5)

Tuesday's Change

Idenix Pharmaceuticals (Nasdaq: IDIX)

**

(46.9%)

China Sky One Medical (Nasdaq: CSKI)

****

(31.2%)

National Bank of Greece (NYSE: NBG)

****

(14%)

Source: wsj.com.

The devil's in the details
On a day when the market fell 1.07%, Tuesday's declines that exceeded that by a wide margin are big deals.

Like ImmunoGen (Nasdaq: IMGN) last week, the shares of Idenix Pharmaceuticals got hammered yesterday as a result of action from the Food and Drug Administration. Unlike the biotech however, there doesn't seem to be a clear way out of this mess. Immunogen will simply have to take its drug through late-stage trials before it can be considered by the agency, something it would have had to do anyway; Idenix on the other hand faces a major roadblock.

The pharmaceutical said U.S. regulators were halting further testing of two of its hepatitis C drugs because of safety concerns. It hasn't gotten a formal letter just yet, but the severity of the outcomes witnessed thus far apparently spurred the FDA to action. Yet analysts think that one of the two drugs, IDX184, will still make it through the review, but the second therapy, IDX320, will not.

Wall Street had been unanimous in its belief that Idenix would outperform the broad market averages, and while only 88% of CAPS members rating it thought it would, the adverse reactions to its treatments probably even surprised the naysayers. Let us know on the Idenix Pharmaceuticals CAPS page if you think it will prevail.

The sky's not the limit
Still reeling from allegations of financial shenanigans, China Sky One Medical hit investors with a new revelation on Friday, after the market's close, that it was cutting its guidance for the year because several major distributors had ceased doing business with it. The nutritional supplement maker says it was because the distributors learned it would have to disclose information about their business to the SEC in regulatory filings, but for a company that's already accused of fraudulent practices, investors might be right to wonder about the timing of the latest revelation. Oh, and its chief financial officer abruptly resigned, too.

CAPS All-Star FleaBagger is right to question whether this is a prelude to further accounting fraud like that which sunk Mahindra Satyam (NYSE: SAY). Companies that dump really bad news on Friday afternoons, particularly on long holiday weekends, are worth scrutinizing much more closely, because good results rarely come out of such attempts at burying the news.

Don't bring me down
As Jordan DiPietro points out, it was a well-known secret that the European bank stress tests were simply a paper tiger, a facade put up to try to restore confidence in a system that was badly shaken by the potential for sovereign defaults. Yet the latest revelations are cutting the legs out from underneath even that most flimsy of rationales.

Not only did banks like Barclays fail to disclose the true level of government debt they held, the government of Greece is now being accused of lying about the extent to which it used secret transactions to hide its debt. National Bank of Greece was hit hard as a result, even though it gamely says it doesn't think its government will default.

Investors aren't so sure, and they're bidding up yields on the country's debt as a result. That's happening in Ireland, too, where fears of an implosion are causing spreads to rise to record levels. Allied Irish Banks (NYSE: AIB) and Bank of Ireland (NYSE: IRE) are roiled as doubts about the government's commitment to them, even after nationalizing them and infusing them with billions of dollars, grows. But with worries about Greece back in the headlines, National Bank of Greece, even with seemingly superlative Tier 1 capital ratios, remains a risky bet.

Some CAPS members, though, think that by focusing only on the headline news, you'll miss an excellent investment opportunity. danj585 points to the bank using the stronger Turkish economy to prop up its operations as a reason it will outperform:

While the bank is the National Bank of Greece, where the troubled nation will scare some investors off, much of their holdings are in Turkey. Turkey's economy is doing very well. This could be a profitable sleeper as the economy improves.

Ready for a resurrection
Just because your stock has taken a beating doesn't mean it's going to roll over and die. Markets are known for overreacting. A closer look at what's happened to your stock can give you an edge over other investors who just react to the market's lead.

That's why it pays to start your own research on these stocks on Motley Fool CAPS, where you can read a company's financial reports, scrutinize key data and charts, and examine the comments your fellow investors have made, all from the stock's CAPS page. Then you can decide for yourself whether it's ready to come back from the dead.

The Fool owns shares of National Bank of Greece. Try any of our Foolish newsletter services free for 30 days.

True to its name, The Motley Fool is made up of a motley assortment of writers and analysts, each with a unique perspective; sometimes we agree, sometimes we disagree, but we all believe in the power of learning from each other through our Foolish community. The Motley Fool has a disclosure policy.

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings. The Motley Fool has a disclosure policy.