Battered by a long-running patent dispute and fears of competition, Research In Motion ( RIMM) has had one solid defense in recent quarters: its standout growth rate.

Now that shield may be going away.

The company warned on Wednesday that subscriber additions to its BlackBerry service will come in lower than anticipated in the next two quarters. RIM blamed the shortfall on the late rollout of two new BlackBerry devices.

But investors and buy-side analysts aren't buying the argument. Instead, they see something much more portentous: the beginning of an inevitable slowdown in RIM's growth rates. If they're right, the development could have big implications for the company's stock price.

Indeed some former bulls have recently gone short RIM shares and others are considering doing the same.

You can put Scott Rothbort, president of LakeView Asset Management and a contributor to TheStreet.com's sister site Street Insight, in that latter camp.

"I don't see where this company is going," says Rothbort, who currently has no position in RIM's shares. "There's no good news over at RIM."

Instead, on Wednesday the company offered more bad news. The company said it expects subscriber additions in its current quarter will come in 8% lower than its expected range of 680,000 to 710,000. For its fourth quarter, the company expects subscriber additions to be 3% lower than its previously forecasted range of 775,000 to 825,000.

Shares of RIM closed regular trading on Wednesday off 80 cents, or about 1%, to $66.28. Earlier in the session, following the announcement, they were off as much as 7% before bouncing back.

Some investors and analysts are beginning to believe that things are likely to get worse for RIM. The slashed forecasts mark the second time in three months that the company has had disappointing news on the subscriber front. Subscriber additions in the second quarter came in at the low end of the company's expected range.

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