Research In Motion Ltd. (Nasdaq: RIMM) plunged the most in 11 weeks after saying revenue missed its forecast last quarter amid accelerating market-share losses for BlackBerry smartphones and PlayBook tablets to Apple Inc. (Nasdaq: AAPL)

Third-quarter revenue was “slightly lower” than the $5.3 billion to $5.6 billion the company had projected and earnings were “at the low to mid point” of its forecast, according to an unscheduled statement from Waterloo, Ontario-based RIM today. RIM said it doesn’t expect to meet its full-year profit target.

The shortfall — the fourth straight quarter sales missed analysts’ estimates — puts more pressure on co-Chief Executive Officers Jim Balsillie and Mike Lazaridis as they seek to revive a company that once dominated the U.S. smartphone market. RIM’s market-share decline has prompted investors such as Jaguar Financial Corp. to call for a change in leadership and for RIM to divide into separate companies or seek a sale.

“The next question from a management perspective is do they need someone different? They cannot keep going on the same course forever,” said Bahl & Gaynor Investment Counsel’s Matt McCormick, whose firm oversees $4.1 billion. McCormick, speaking from Cincinnati, said he’s “glad” his firm doesn’t own RIM stock.

RIM fell 8.7 percent to $16.97 at 10:16 a.m. New York time after dropping as much as 9.9 percent, the most since its previous sales miss in September. The stock had lost 68 percent this year before today, while Apple advanced 20 percent.

PlayBook Slump

RIM will record a $485 million pretax provision to revalue the inventory for the PlayBook tablet, which has failed to win over users in a market dominated by Apple’s iPad. RIM said more promotions are needed to drive demand for its tablet, whose shipments fell (RIMM) to 150,000 units last quarter, less than a third of the 500,000 tablets RIM shipped in the first quarter after they went on sale in May. In its most recent quarter, Cupertino, California-based Apple sold a record 11.12 million iPads.

“When the PlayBook is supposed to be the savior and it’s not, where do you go,” McCormick said.Research In Motion (Nasdaq: RIMM), the struggling maker of the BlackBerry phones, is writing off much of its inventory of PlayBook tablets, since it has to sell them at a deep discount.

The Canadian company, which operates a research and development office in the Triangle, said that it’s taking a pre-tax charge of $485 million in the just-ended quarter to account for the declining value of the tablets. The model originally priced at $500 now costs $200.

RIM launched the tablet this spring. Reviewers puzzled over the lack of email software, saying the device seemed half-baked. RIM now promises updated software in February.

(Bloomberg and The AP contributed to this report.)

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