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 wind-turbine component maker American Superconductor (Nasdaq: AMSC) plunged 18% today after delaying the filing of its annual report.

So what: The shares were absolutely pummeled in early April after American Superconductor slashed its full-year revenue outlook to under $355 million on news that its largest customer, Sinovel, refused to accept contracted shipments. However, with the company's disclosure last night that it needs more time to review its sales from customers in China and that it expects a "material amount of revenue" to be reversed, Mr. Market is obviously worried that even the $355 million forecast might be high.

Now what: I'd be cautious about pouncing on today's plunge. Given that Sinovel accounts for a whopping 75% of American Superconductor's business, there could still be plenty of pain ahead if no resolution is reached. Throw in the fact that management also announced a hiring freeze and that it is reviewing options to secure additional financing -- to complete its $273 million purchase of Finnish rival The Switch Engineering Oy -- and it's clear that American Superconductor has a bit too much uncertainty for most investors to handle.

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

Fool contributor Brian Pacampara owns no position in any of the companies mentioned. Try any of our Foolish newsletter services free for 30 days.

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 Fool's disclosure policy always gets a perfect score.