text: Research in Motion already has to deal with falling BlackBerry sales and a disappointing roll-out of its PlayBook tablet. Will it now have to fend off Carl C. Icahn as well?
  
  Shares in the wireless device maker jumped as much as 7 percent on Tuesday amid speculation that the billionaire investor had taken a stake in RIM. The company’s stock traded at $23.01 by early afternoon, still up 6 percent.
  
  Beset by the growing popularity of the iPhone and an armada of Android-based devices, RIM has been suffering for some time. The company’s stock has plummeted more than 60 percent so far this year, giving it a market value of just $12 billion.
  
  It is not clear what Mr. Icahn would call on RIM to do. The company insists that it will forge ahead with new devices based on a next-generation operating system, rather than on more drastic courses of action like an asset sale.
  
  At least one other activist investor, Jaguar Financial, is calling on RIM to consider strategic options that may include the sale of the company’s patent portfolio. (Analysts at Jefferies & Company are not very optimistic about the prospects of such a move, saying that it could fetch as little as $1 billion.)
  
  Then again, Mr. Icahn, a longtime activist investor, has a record of spurring positive change at cellphone makers.
  
  After his repeated prodding, Motorola agreed to split itself into two divisions, one that makes handsets and one that manufactures enterprise equipment. Last month, the handset maker agreed to sell itself to Google for $12.5 billion.
  
  Mr. Icahn was not immediately available for comment.
summary: Is Research in Motion in Carl C. Icahn's cross hairs? Shares of the BlackBerry maker jumped as much as 7 percent amid speculation that he had taken a stake in the company.