Corning (GLW) was getting hammered in the market Tuesday, with shares down more than 13% in afternoon trading.

The company was forced to lower its fourth-quarter profit estimates after a major customer said it wasn't going to buy as many glass displays as it had promised. Now, Corning has cut its production outlook for the glass it makes for LCD displays.

The company's main problem is that there's too much supply. Corning tried to address that by cutting its LCD glass prices, but that wasn't enough to keep its major customer on board.

Corning's other problem is the iPad. Corning makes a "Gorilla Glass" for smartphones and tablet computers, but is seeing lower global demand for cover glass for tablet computers. So Corning lowered its Gorilla Glass sales forecast for the quarter to a 25% sequential drop from the original estimate of a 15% drop.

The company's shares fell more than 13% to $12.81 in afternoon trading. With Tuesday's drop, the stock has fallen some 33% this year.

Apple (AAPL) doesn't say who its glass suppliers are, but it appears that Corning is no longer one of them. Apple has reportedly turned to Asian suppliers Lens Technology, G-Tech and Fuji Crystal for the glass in its iPhones and iPads.

Corning also had some bad news for its joint venture with Samsung Electronics. The venture will probably only make 5% to 10% more glass this quarter, where it had originally expected at least a 20% increase.

And Corning's overall LCD glass volume will now be up only slightly sequentially. Previously, the company guided to at least a 10% increase.

Finally, consolidated equity earnings will likely be down 30%, a big plunge from the original expectation of a 5% drop.

It doesn't sound like things will improve much in the near term. Glass price declines will continue. Corning will reduce capacity by idling its glass melting tanks already down for repair and delaying the start of new tanks.

But Corning put a positive spin on the news, saying it expected long-term improvements once the supply glut is under control.

"While we are clearly facing some headwinds this quarter, we are not changing our long-term growth expectations for the company," the company said in a statement. "Our goal to grow company sales to $10 billion is still well on track with all of our segments growing." Corning reported $2.1 billion in sales for the third quarter.

And at least one analyst is still bullish. Drake Johnstone of Davenport & Co., who just Monday raised his rating on Corning to buy from hold, said he thinks retail demand for LCD televisions is holding up well. Corning said that worldwide LCD TV unit sales grew 12% in September. In the U.S. alone, LCD TV sales rose 13% in September and 4% in October.

"Provided that global LCD television unit growth remains at 10%+ year-over-year in 2012, we believe that panel maker demand for Corning's glass substrates should improve in the first half of 2012," Johnstone wrote Tuesday in a note obtained by Barron's.

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