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 solar powerhouse (and Total (NYSE: TOT) subsidiary) SunPower (Nasdaq: SPWRA) ended Monday down 12%, hurt by a cryptic note from the company's CFO, who warned that SunPower plans to "revise" its full-year earnings forecast when it reports earnings on Nov. 3.

So what: SunPower didn't specifically say that earnings will be revised down -- but that was the clear implication. The CFO mentioned "challenging market conditions," and challenging is rarely a good adjective when used in the context of earnings forecasts.

Now what: I won't say "I told you so" (but I did). Reviewing the company's numbers last month, I described how even an optimistic reading of the stock made it look pricey at "47 times earnings." (Make that 27 times earnings, now that the stock has fallen so far.) Meanwhile, a more skeptical examination revealed that the company was not really "earning" anything at all -- but rather "burning cash at the rate of $155 million annually."

That's still my opinion, and I'm sticking to it.

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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.