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 Quantum (NYSE: QTM) have tanked today by as much as 30% after the company reported preliminary earnings that fell short of expectations.

So what: The company said it expects revenue to land right at $141 million, generating an adjusted net loss of between $0.03 and $0.04 per share. That's worse than the guidance it provided back in May as well as the Street consensus of $155 million in sales and a breakeven bottom line.

Now what: Quantum cited weakness in Europe and trouble closing big deals near the end of the quarter as the culprit for the shortfall. CEO Jon Gacek said the company was seeing sales momentum but it wasn't enough to overcome its challenges. Its official earnings release will be on July 31. This adds additional fodder to the broader worries of soft IT spending, particularly in Europe as macro uncertainties continue to weigh.

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Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.