After a fantastic run, BlackBerry maker Research In Motion ( RIMM) is finally showing signs of slowing.

Shares of RIM dropped 4%, or $5.42, to $130.01 after two analysts issued research notes suggesting that there may be little upside left in the stock.

Based on concerns over the stock price and the company's plans to launch new products to keep up growth in the consumer business, Morgan Keegan analyst Tavis McCourt downgraded the stock to market perform from outperform.

"We believe the uncertainty with respect to the potential need to accelerate operating expenses to support a larger consumer business as well as the 'hits'-driven nature of the business warrant some caution," he wrote in his note. Morgan Keegan does not have a banking relationship with RIM.

RBC Capital Markets, which has a banking relationship with Ontario, Canada-based RIM, has also downgraded the stock.

RIM has pulled back 4% since it reached its 52-week high on Nov. 24, touching $141.69. However, it has seen one of the biggest market run-ups this year, rising 66% in the three months since Sept. 7, and 112% in a year.

"The valuation is finally starting to matter to some analysts," says Robert Lawton, a portfolio manager with Catoosa Fund, which has a short position in RIM. Any hint of weakness in the company's third-quarter results to be announced Dec. 21, and the market sentiment could turn against RIM, he says.

Other fund managers have been suggesting in recent few weeks that at this stage, the rally in RIM's shares may have more to do with the momentum in the market than the company's fundamentals.

Meanwhile, a Canadian pension fund is threatening action against RIM for ignoring its concerns over the company's investigation of its historical stock option grant practices.

The Ironworkers Ontario Pension Fund, which owns a position in RIM slightly in excess of $1.75 million, has through its lawyers called on RIM to broaden the scope of its investigation and dismiss RIM's audit committee, which the fund alleges has a strong conflict of interest.