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 trucker YRC Worldwide (Nasdaq: YRCW) crashed hard today, falling as much as 30% in intraday trading on heavier-than-average volume.

So what: This new round of selling comes on the heels of the release of YRC's annual 10-K filing, which noted that the company had missed the deadline to get approval for its restructuring from certain pension funds. Technically, the missed deadline could be used by YRC's lenders to declare the company in default, which would likely push YRC into bankruptcy. So there's good reason for equity holders to be a bit spooked.

Now what: As YRC noted in the 10-K, the lenders have not yet indicated they're going to declare the company in default, and that may not be all that surprising since the lenders have been working with the company to keep it out of bankruptcy for a couple of years now. Of course with many parties involved in these restructuring negotiations, it's very possible that the lenders will eventually hit a point where they realize that bankruptcy courts will be the best place to sort this all out.

Earlier in the month, investors saw YRC shares dive after management suggested that the restructuring plan could mean "very substantial dilution" for shareholders. Taken along with the bankruptcy risk, it would seem that YRC investors are between a rock and a bottomless canyon.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.